Kvantfysik
[1]
Uppdaterad: 171211
Har jag använt någon bild som jag inte får använda? Låt mig veta så tar jag bort den.christian.karlsson@ckfysik.se
[1] Läget runt 1920
[2] Materiens vågegenskaper (de Broglie)
[3] Men kan det vara så här? (Elektroner och gitter)
[4] Men kan det vara så här? (Elektroner och dubbelspalt) [5] Materiens vågegenskaper (Schrödinger – Born)
[6] Kvantmekanik (tidig) [7] Kvantmekanik (tidig)
[8] Heisenbergs obestämdhetsrelation [9] Läget runt 1927
[10] Efter 1927 [11] Läget idag
[12] Läget idag i ∂ ψ
∂t = −
22m
∂
2ψ
∂x
2+U ψ
[2]
Kvantfysik
[3]
[4]
X
Richard Feynman
Märklig och ointuitiv – men inte ologisk!
Do not keep saying to yourself, if you can possibly avoid it,
”But how can it be like that?” because you will get ”down the drain”, into a blind valley from which nobody has yet escaped.
Nobody knows how it can be like that.
Niels Bohr
But, but, but ... if anybody says he can think about quantum theory without getting giddy it merely shows that he hasn’t understood the first things about it!
[5]
[6]
FSS
Några milstolpar i fysiken
Newton (Principia)
Young (Dubbelspaltexpt.) Maxwell (E och M)
Thomson (elektronen) Planck (energikvanta) Einstein (ljusenergi
kvantiserad) Bohr (ny atommodell)
1687
~1803
~1864 1897 1900 1905
1913 Spec. rel.teori
[7]
X
Några milstolpar i fysiken
Newton (Principia)
Young (Dubbelspaltexpt.) Maxwell (E och M)
Thomson (elektronen) Planck (energikvanta) Einstein (ljusenergi
kvantiserad) Bohr (ny atommodell)
1687
~1803
~1864 1897 1900 1905
1913 Spec. rel.teori
[7]
X
Läget runt 1920
X
[8]
FSS
Läget runt 1920
1
Partikelegenskaper Vågegenskaper
Materia
Strålning
Ja! (mekanik)
p = mv
W
k= mv
22
p =
γ
mv Ek = (γ
−1)mc2 R = pJa! (fotonmodellen)
?
light!waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig.3. The light source is a 5 mW green!!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors !all 1 in. optics" arranged in a 18
"18 cm2square !see Figs.2and3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1.!Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
light !waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig.3. The light source is a 5 mW green!!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors!all 1 in. optics" arranged in a 18
"18 cm2 square!see Figs.2 and3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1.!Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
[9]
Ja! (elektromagnetism, optik)
W = hfp = h
λ
E, BDubbelspaltexperiment med fotoner (2005)
FSS
Läget runt 1920
X
light !waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig. 3. The light source is a 5 mW green !!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors !all 1 in. optics" arranged in a 18
"18 cm2 square !see Figs. 2 and 3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1. !Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
[9]
FSS
Materiens vågegenskaper
[10]
2
de Broglie (1924):
Varje partikel kan tillskrivas en våglängd λ = h p
Plancks konstant
partikelns rörelsemängd
“materievåglängd”
[11]
p = h
λ ⇒ λ = h Fotoner: p
Einstein (1916):
Materiens vågegenskaper
[10]
Ger en slags förklaring till
väteatomens kvantiserade energinivåer:
2
de Broglie (1924):
Varje partikel kan tillskrivas en våglängd λ = h p
Plancks konstant
partikelns rörelsemängd
“materievåglängd”
[11]
villkoret
2 π r = n λ
måste vara uppfylltp = h
λ ⇒ λ = h Fotoner: p
Einstein (1916):
Jfr stående våg på sträng:
Materiens vågegenskaper
[10]
Ger en slags förklaring till
väteatomens kvantiserade energinivåer:
2
de Broglie (1924):
Varje partikel kan tillskrivas en våglängd λ = h p
Plancks konstant
partikelns rörelsemängd
“materievåglängd”
Bekräftades 1927
G. P. Thomson (UK)
Davisson & Germer (USA)
[11]
[13]
[12]
villkoret
2 π r = n λ
måste vara uppfylltp = h
λ ⇒ λ = h Fotoner: p
Einstein (1916):
Jfr stående våg på sträng:
Men kan det vara så här?
3
FSS
Men kan det vara så här?
Elektronkanon
3
Uacc
+ –
Glödtråd e–
FSS
Men kan det vara så här?
Vitt ämne som fluorescerar i grönt
när det träffas av elektroner.
Elektronkanon
3
Uacc
+ –
Glödtråd e–
FSS
Men kan det vara så här?
Tunt lager av grafit. Fungerar som ett gitter*
för elektronerna (p.g.a. den regelbundna atomstrukturen).
Vitt ämne som fluorescerar i grönt
när det träffas av elektroner.
Elektronkanon
3
Uacc
+ –
Glödtråd e–
FSS
Men kan det vara så här?
Tunt lager av grafit. Fungerar som ett gitter*
för elektronerna (p.g.a. den regelbundna atomstrukturen).
Vitt ämne som fluorescerar i grönt
när det träffas av elektroner.
Elektronkanon
3
Uacc
+ –
Glödtråd e–
Ringar – partiklar har vågegenskaper!
FSS
[14]
[16]
[15]
4
Men kan det vara så här?
Dubbelspaltmönster med elektroner har observerats!
[17]
https://www.youtube.com/watch?v=5oQWtcfZN4M
FSS
Materiens vågegenskaper
5
Elektronen – våg eller partikel?
https://www.youtube.com/watch?v=mhfdwH5Kdbc
Jämför med ljusinterferens:
sannolikheten att en elektron träffar ett visst ställe är fördelad som
intensitetsfördelningen från en våg som passerat dubbelspalten
e–-kanon
Dubbelspalt Skärm
Intensitet
Läge
Materiens vågegenskaper
5
Elektronen – våg eller partikel?
https://www.youtube.com/watch?v=eCFTVdExxPA
Elektroner – sänds ut och detekteras som partiklar – sannolikheten att hitta en elektron någonstans beskrivs med en våg
Jämför med ljusinterferens:
sannolikheten att en elektron träffar ett visst ställe är fördelad som
intensitetsfördelningen från en våg som passerat dubbelspalten
e–-kanon
Dubbelspalt Skärm
Intensitet
Läge
Ingetdera!
Kvantmekanik (tidig)
http://www.youtube.com/watch?v=8GZdZUouzBY
Matematik ¨ar vackert – tre exempel
Arean A under kurvan y = x2 mellan x = 0 och 1:
A =
⇧1
0
x2dx =
⇤x3 3
⌅1 0
= 1
3 (1)
1 0,5
0,5 1
y
A
y = x2
x
Samband mellan e = 2.71828 . . ., i som ¨ar s˚adant att i2 = 1 och ⇥ = 3.14159 . . .:
ei = 1 (2)
V˚agfunktionen f¨or en elektron i f¨orsta skalet i en v¨ateatom (f˚as om man l¨oser Schr¨odingerekvationen f¨or v¨ateatomen):
⇤100(r) = 1
⇥⇥ 1 a0
⇥32
e a0r , (3)
d¨ar
a0 = 4⇥ 0 2
µe2 . (4)
Sannolikheten att hitta elektronen mellan avst˚anden R2 och R1
(fr˚an k¨arnan):
P (R2, R1) = 4⇥
R2
⇧
R1
r2⇤1002 dr (5)
6
I kvantmekaniken (1925-26) beskrivs partiklar med vågfunktioner ψ( x,t)
har att göra med sannolikheten att hitta en partikel i (x, t)
Schrödinger
0 0,05 0,1 0,15
0 1 2 3 4 5
y =x2e−2 x
[22]
Heisenberg
Born Dirac
(en formulering av)
[21]
[20]
[18] [19]
FSS
Solvay-konferensen 1927
X
[23]
FSS
http://www.youtube.com/watch?v=8GZdZUouzBY
X
Solvay-konferensen 1927
[24]
FSS
http://www.youtube.com/watch?v=8GZdZUouzBY
X
Solvay-konferensen 1927
42 år 25 år
44 år 35 år
48 år
27 år 40 år
69 år
35 år
[24]
FSS
Kvantmekanik (tidig) vs. klassisk mekanik
7
Klassisk mekanik
Kvantmekanik
x(t)
ψ(x,t)
R = m d
2x dt
2i ∂ψ
∂t = −
22m
∂
2ψ
∂x
2+U ψ
Lägesfunktion
Vågfunktion
Sannolikheten att hitta partikeln mellan x
1och x
2:
P(x
1, x
2) = |ψ |
2dx
x1 x2
∫
Newton II
Schrödingerekvationen
Representerar omgivningens inverkan
1
0 2 3 4 5 m
x
m R
FSS
X
Kvantmekanik (tidig)
[25]
FSS
Inte bara elektroner ...
X
Neutroner, He-atomer, C
60-molekyler och...
FSS
Inte bara elektroner ...
[27]
X
[26]
... ftalocyanin:
Neutroner, He-atomer, C
60-molekyler och...
(STM-bilder)
FSS
Inte bara elektroner ...
[27]
Real-time single-molecule imaging of quantum interference
Thomas Juffmann1, Adriana Milic1, Michael Mu¨llneritsch1, Peter Asenbaum1, Alexander Tsukernik2, Jens Tu¨xen3, Marcel Mayor3,4, Ori Cheshnovsky2,5and Markus Arndt1*
The observation of interference patterns in double-slit exper- iments with massive particles is generally regarded as the ulti- mate demonstration of the quantum nature of these objects.
Such matter–wave interference has been observed for electrons1, neutrons2, atoms3,4and molecules5–7and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the “most beautiful experiment in physics”8–11. Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum inter- ference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514AMU and 1,298AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10 nm and revealed the build-up of a determi- nistic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave–particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics.
When Richard Feynman described the double-slit experiment with electrons as being ‘at the heart of quantum physics’12he was emphasizing how the fundamentally non-classical nature of the superposition principle allows the quantum wavefunction associ- ated with a massive object to be widely delocalized, while the object itself is always observed as a well-localized particle. Recent experiments have focused this discussion by demonstrating the stochastic build-up of interference patterns11,13, by implementing double-slit diffraction in the time domain14,15(including down to the attosecond level16), and by identifying a single molecule as the smallest double-slit for electron interference17,18that enables funda- mental studies of decoherence19. The extension of this work20to large molecules requires a sufficiently intense and coherent beam of slow and neutral molecules, a nanoscale diffraction grating, and a detector that offers a spatial accuracy of a few nanometres and a molecule-specific detection efficiency of close to 100%. We achieve that in this work with a combination of micro-evaporation, nanofabrication and nano-imaging.
Our experimental set-up comprises three sections: beam prep- aration, coherent manipulation and detection (Fig. 1). The molecules
need to be prepared such that each one interferes with itself, and all lead to similar interference patterns on the screen. Because the trans- verse and longitudinal coherence functions are determined by the Fourier transforms of the source spatial extension and velocity distri- bution21, we require a good collimation and velocity selection. Under
‘far-field’ conditions we can approximate the molecular wave- functions as plane waves, and the angle unof the nth order diffraction peak is given by the equation sin un¼ nL/d, where L ¼ h/mv is the de Broglie wavelength, h is Planck’s constant, m is the particle mass, v is the velocity, and d is the period of the diffraction grating.
Massive particles therefore need to be slow to achieve sizable diffrac- tion angles. Although deceleration techniques have been advanced for molecules even as complex as benzonitrile22, effusive beams (Fig. 1b) are still well suited for preparing slow beams of particles a hundred times more massive than that23,24.
For thermolabile organic molecules, which may decompose when heated to their evaporation temperature, we use a laser micro-source (Fig. 1a), which reduces the heat load to a minimum. A blue diode laser is focused onto a thin layer of molecules deposited on the inside of the entrance vacuum window W1, which can be moved by a motorized translation stage. Although high temperatures can be reached locally, this affects only the particles within the focus area. In comparison to a Knudsen cell, the heat load to the sample is therefore reduced by two to three orders of magnitude (to several 10 mW). Spectral coherence is achieved by sorting the arriving molecules according to their longitudinal velocity and their respective freefall height in the Earth’s gravitational field25.
The collimation slit S defines the spatial coherence of the mole- cular beam. The slit and the grating width further downstream narrow the beam divergence to less than the diffraction angle. The grating is machined into a thin SiNxmembrane and has a period of d ¼100 nm. To minimize the dispersive van der Waals inter- action between the molecules and the grating wall we reduce the grating thickness from 160 nm (as in earlier diffraction experi- ments5,20) to as little as 10 nm in our present set-up. This is impor- tant for the manipulation of complex molecules, which may exhibit high polarizabilities, permanent and even thermally induced electric dipole moments26,27. Each individually diffracted molecule finally arrives at the 170-mm-thin quartz plate W2, which seals the detector vacuum chamber against ambient air. The gradual emergence of the quantum interference pattern is then observed by means of wide- field fluorescence microscopy of W2.
Imaging of single molecules in the condensed phase began about two decades ago28, and various methods for subwavelength optical imaging have been developed since29. Here, we make use of a scheme that is similar to single-molecule high-resolution imaging
1Vienna Center of Quantum Science and Technology, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria,2The Center for Nanoscience and Nanotechnology, Tel Aviv University, 69978 Tel Aviv, Israel,3Department of Chemistry, University of Basel, St. Johannsring 19, 4056 Basel, Switzerland,4Karlsruhe Institute of Technology, Institute for Nanotechnology, PO Box 3640, 76021 Karlsruhe, Germany,5School of Chemistry, The Raymond and Beverly Sackler faculty of exact sciences, Tel Aviv University, 69978 Tel Aviv, Israel.*e-mail: markus.arndt@univie.ac.at
LETTERS
PUBLISHED ONLINE: 25 MARCH 2012 |DOI: 10.1038/NNANO.2012.34
NATURE NANOTECHNOLOGY| ADVANCE ONLINE PUBLICATION | www.nature.com/naturenanotechnology 1
X
[26]
... ftalocyanin:
[28]
Neutroner, He-atomer, C
60-molekyler och...
(STM-bilder)
FSS
Heisenbergs obestämdhetsrelation
8
Heisenberg (1927):
Omöjligt att bestämma en partikels läge och rörelsemängd samtidigt!
Δp
x⋅ Δx ≥ h 4π
oskärpa i rörelsemängd
oskärpa i läge
[29]
[30]
Heisenbergs obestämdhetsrelation
8
Heisenberg (1927):
Omöjligt att bestämma en partikels läge och rörelsemängd samtidigt!
Δp
x⋅ Δx ≥ h
4π Ex: Ljus genom enkelspalt
oskärpa i rörelsemängd
oskärpa i läge
Δx
Δp
xp
[29]
[30]
Använd fotonmodellen och betrakta en foton i spaltöppningen. Fotonens rörelsemängd är
Minska spaltbredden
→ mindre Δx → större Δp
x→ mer utsmetad intensitetsfördelning
p
Heisenbergs obestämdhetsrelation
8
Heisenberg (1927):
Omöjligt att bestämma en partikels läge och rörelsemängd samtidigt!
Δp
x⋅ Δx ≥ h
4π Ljus genom enkelspalt
Använd fotonmodellen och betrakta en foton i spaltöppningen. Fotonens rörelsemängd är
Minska spaltbredden
→ mindre Δx → större Δp
x→ mer utsmetad intensitetsfördelning Ex:
oskärpa i rörelsemängd
oskärpa i läge
Δx
Δp
xp
Jfr vågmodellen:
[29]
[30]
p
Läget runt 1927
9
Partikelegenskaper Vågegenskaper
Materia
Strålning
Ja! (mekanik)
p = mv
W
k= mv
22
p =
γ
mv Ek = (γ
−1)mc2 R = pJa! (fotonmodellen)
light!waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig.3. The light source is a 5 mW green!!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors !all 1 in. optics" arranged in a 18
"18 cm2square !see Figs.2and3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1.!Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
light !waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig.3. The light source is a 5 mW green!!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors!all 1 in. optics" arranged in a 18
"18 cm2 square!see Figs.2 and3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1.!Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
[9]
Ja! (elektromagnetism, optik)
W = hfp = h
λ
E, BJa! (kvantmekanik) i ∂ψ
∂t = −
22m
∂
2ψ
∂x
2+U ψ
FSS
Dubbelspaltexperiment med fotoner (2005)
λ
= h pEfter 1927?
10
2000 2010 2020 2030 2040 1900
1890 1910 1920 1930 1940
1880 1950 1960 1970 1980 1990
Tidig kvant- mekanik Kvantfysik
Kvantkemi, materialfysik
Atomfysik, kärnfysik, partikelfysik
QED QCD
Relativistisk kvantmekanik, kvantfältteori
FSS
Efter 1927?
X
FSS
Efter 1927?
10
2000 2010 2020 2030 2040 1900
1890 1910 1920 1930 1940
1880 1950 1960 1970 1980 1990
Tidig kvant- mekanik Kvantfysik
Kvantkemi, materialfysik
Atomfysik, kärnfysik, partikelfysik
QED QCD
Relativistisk kvantmekanik, kvantfältteori
FSS
Vägintegralformulering (Feynman) Matrismekanik (Heisenberg, Dirac)
Vågmekanik (Schrödinger)
Efter 1927?
10
2000 2010 2020 2030 2040 1900
1890 1910 1920 1930 1940
1880 1950 1960 1970 1980 1990
Tidig kvant- mekanik Kvantfysik
Partikelfysikens standardmodell Kvantkemi, materialfysik
Atomfysik, kärnfysik, partikelfysik
QED QCD
Relativistisk kvantmekanik, kvantfältteori
[31] [32]
FSS
Efter 1927?
X
2000 2010 2020 2030 2040 1900
1890 1910 1920 1930 1940
1880 1950 1960 1970 1980 1990
Tidig kvant- mekanik Kvantfysik
Partikelfysikens standardmodell Kvantkemi, materialfysik
Atomfysik, kärnfysik, partikelfysik
QED QCD
Relativistisk kvantmekanik, kvantfältteori
[31] [32]
FSS
11
Läget idag
[33]
FSS
Ett sätt at se på det:
light!waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig.3. The light source is a 5 mW green!!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors !all 1 in. optics" arranged in a 18
"18 cm2square !see Figs.2and3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1.!Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
light !waves and particles" are mutually exclusive because they appear independently in different experiments. To elimi- nate this conceptual difficulty we have designed an apparatus in which the particle and wave aspects can first be demon- strated individually. Then the same apparatus is used to vi- sualize the real-time evolution of individual quantum events to a classical wave pattern. The use of the same light source and the same interferometer is important to convince stu- dents that we can investigate the two aspects of light with the same apparatus.
Two-beam interference phenomena are often explained on the basis of Young’s double slit experiment by displaying the well known interference pattern on a distant screen. Al- though this example is well suited for a theoretical discus- sion and most easily realized using a laser pointer and a double slit, it is not practical for advanced demonstration experiments because it does not allow the variation of system parameters in a simple way. In the present experiment we have chosen a Mach-Zehnder interferometer in which a large spatial separation of the two interfering beams can be easily realized, permitting several manipulations, such as the ad- justment of the path length difference and the relative angle of the interfering beams, and, most importantly, the easy blocking of one of the two beams. The macroscopic dimen- sions of the Mach-Zehnder interferometer allow the observer to see all components from the light source via the genera- tion and recombination of the interfering beams up to their detection.
A green laser pointer was chosen as the light source be- cause it has a sufficiently long coherence length for the easy alignment of the interferometer. The intensity of the green beam and its wavelength near the vicinity of the eye’s maxi- mum sensitivity ensure that even expanded interference pat- terns are easily visible in a large auditorium.
Our main design criterion was to have the apparatus as simple and pedagogical as possible while also offering the flexibility to vary certain parameters to illustrate several as-
pects of the phenomena. The equipment is designed for dem- onstrations in a large auditorium. The interferometer is mounted on an aluminum plate tilted by 45°, so that all com- ponents can be easily seen. If necessary, a webcam can be used to project a close-up of the interferometer table. As mentioned, the expanded fringe pattern using the full laser intensity can easily be seen from a distance without addi- tional tools. Individual photon events can be seen as pulses on an oscilloscope, or heard as clicks using audio equipment.
All relevant electronic signals !photomultiplier pulses and photodiode signals" can easily be projected using equipment such as a digital oscilloscope equipped with a video port or a USB-based oscilloscope. Attention was paid to obtain stable pictures and good visibility of all the components and pro- jected signals. Last but not least, we have made an effort to reduce component cost as much as possible, and to give the apparatus a pleasant look.
III. EXPERIMENTAL SETUP
The scheme of the experimental apparatus is shown in Fig.
2 and a photo of its main components in Fig.3. The light source is a 5 mW green!!=537 nm" laser pointer. The bat- teries in the laser pointer were replaced by electrical contacts so that the laser could be driven by an external power supply.
We found that the spectral width of the laser radiation and hence its coherence length depends on the operating voltage and a randomly chosen pointer has its own optimal voltage for the highest fringe contrast. Once set correctly and after a warm-up time of several minutes this voltage gives repro- ducible results on daily basis.
The standard Mach-Zehnder interferometer has two beam splitters and two mirrors!all 1 in. optics" arranged in a 18
"18 cm2 square!see Figs.2 and3". One of the mirrors is mounted on a low-voltage piezotransducer that allows the voltage-controlled variation of the path length difference
!#5 V per fringe".
Fig. 1.!Color online" From particles to waves: Detection of light diffracted from a double slit on a photon by photon basis using a single-photon imaging CCD camera. Although single frames show an apparently random distribution of photon impact points, their integration reveals the classical fringe pattern.
138 Am. J. Phys., Vol. 76, No. 2, February 2008 T. L. Dimitrova and A. Weis 138
[9]
Dubbelspaltexperiment med fotoner (2005)
Läget idag
12
Partikelegenskaper Vågegenskaper
Materia
Strålning
Ja! (mekanik)
p = mv
W
k= mv
22
p =
γ
mv Ek = (γ
−1)mc2 R = pJa! (fotonmodellen) Ja! (elektromagnetism, optik)
W = hfp = h
λ
E, BJa! (kvantmekanik) i ∂ψ
∂t = −
22m
∂
2ψ
∂x
2+U ψ
Kvantfältteorier
QED
QCD Partikelfysikens standardmodell
FSS
Källor
[0] http://researcher.ibm.com/researcher/view_project_subpage.php?id=4252 Fe-atomer på Cu(111).
[0a] http://www.farnamstreetblog.com/2015/01/richard-feynman-knowing-something/
[0b] Richard P. Feynman i The Character of Physical Law (Penguin Books, 1992) s. 129 [1] http://en.wikipedia.org/wiki/File:Richard_Feynman_Nobel.jpg
[1b] http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~30692~1150611:Europe- Från The Times atlas, 1895
[1b2] http://www.massingnickel.se/bussar.html
[1c] T. L. Dimitrova & A. Weis, American Journal of Physics 76 (2008) 137 se också http://photonterrace.net/en/photon/duality/
solvay Se ockås http://www.youtube.com/watch?v=8GZdZUouzBY
[2] http://en.wikipedia.org/wiki/File:Broglie_Big.jpg
[3] http://www.diyphysics.com/2013/04/02/in-memoriam-dr-akira-tonomura-1942-2012/
[4] http://en.wikipedia.org/wiki/File:Erwin_Schrödinger.jpg [5] http://en.wikipedia.org/wiki/File:Phthalocyanine-3D-balls.png [6]
[7]
[8]
[9]
[10]
Vidareläsning
Kapitel 4 i Ett utsökt universum
av Brian Greene Quantum – A Guide for The Perplexed
av Jim Al-Khalili