The Hong–Ou–Mandel interference experiment is a fundamental demonstration of nonclassical interference and a basis for many investigations of quantum information. This experiment involves the interference of two photons reaching a symmetric beamsplitter. When the photons are made indistinguishable in all possible ways, an interference of quantum amplitudes results in both photons always leaving the same beamsplitter output port. Thus, a scan of distinguishable parameters, such as the arrival time difference of the photons reaching the beamsplitter, produces a dip in the coincidences measured at the outputs of the beamsplitter. The main challenge for its implementation as an undergraduate laboratory is the alignment of the photon paths at the beamsplitter. We overcome this difficulty by using a pre-aligned commercial fiber-coupled beamsplitter. In addition, we use waveplates to vary the distinguishability of the photons by their state of polarization. We present a theoretical description at the introductory quantum mechanics level of the two types of experiments, plus a discussion of the apparatus alignment and list of parts needed.

1.
C. K.
Hong
,
Z. Y.
Ou
, and
L.
Mandel
, “
Measurement of subpicosecond time intervals between two photons by interference
,”
Phys. Rev. Lett.
59
,
2044
2046
(
1987
).
2.
F.
Bouchard
,
A.
Sit
,
Y.
Zhang
,
R.
Fickler
,
F. M.
Miatto
,
Y.
Yao
,
F.
Sciarrino
, and
E.
Karimi
, “
Two-photon interference: The Hong–Ou–Mandel effect
,”
Rep. Prog. Phys.
84
,
012402
(
2020
).
3.
Z. Y.
Ou
and
L.
Mandel
, “
Violation of Bell's inequality and classical probability in a two-photon correlation experiment
,”
Phys. Rev. Lett.
61
,
50
53
(
1988
).
4.
Y. H.
Shih
and
C. O.
Alley
, “
New type of Einstein-Podolsky-Rosen-Bohm experiment using pairs of light quanta produced by optical parametric down conversion
,”
Phys. Rev. Lett.
61
,
2921
2924
(
1988
).
5.
J.-W.
Pan
,
D.
Bouwmeester
,
H.
Weinfurter
, and
A.
Zeilinger
, “
Experimental entanglement swapping: Entangling photons that never interacted
,”
Phys. Rev. Lett.
80
,
3891
3894
(
1998
).
6.
D.
Bouwmeester
,
J.-W.
Pan
,
K.
Mattle
,
M.
Wibl
,
H.
Weinfurter
, and
A.
Zeilinger
, “
Experimental quantum teleportation
,”
Nature
390
,
575
579
(
1997
).
7.
J. L.
O'Brien
,
G. J.
Pryde
,
A. G.
White
,
T. C.
Ralph
, and
D.
Branning
, “
Demonstration of an all-optical quantum controlled-not gate
,”
Nature
426
,
264
267
(
2003
).
8.
P.
Kok
,
W. J.
Munro
,
K.
Nemoto
,
T. C.
Ralph
,
J. P.
Dowling
, and
G. J.
Milburn
, “
Linear optical quantum computing with photonic qubits
,”
Rev. Mod. Phys.
79
,
135
174
(
2007
).
9.
R.
Feynman
,
R. B.
Leighton
, and
M.
Sands
,
The Feynman Lectures on Physics
, Vol.
3
(
Addison-Wesley
,
Reading, MA
,
1965
).
10.
A.
Zeilinger
, “
General properties of lossless beamsplitters in interferometry
,”
Am. J. Phys.
49
,
882
883
(
1981
).
11.
C. H.
Holbrow
,
E.
Galvez
, and
M. E.
Parks
, “
Photon quantum mechanics and beamsplitters
,”
Am. J. Phys.
70
,
260
265
(
2002
).
12.
E.
Bocquillon
,
V.
Freulon
,
P.
Degiovanni
,
B.
Placais
,
A.
Cavanna
,
Y.
Jin
, and
G.
Fève
, “
Coherence and indistinguishability of single electrons emitted by independent sources
,”
Science
339
,
1054
1057
(
2013
).
13.
J.
Carivioto-Lagos
,
P. G.
Armendariz
,
V.
Velazquez
,
E.
Lopez-Moreno
,
M.
Grether
, and
E.
Galvez
, “
The Hong-Ou-Mandel interferometer in the undergraduate laboratory
,”
Eur. J. Phys.
33
,
1843
1850
(
2012
).
14.
Qubutekk
, “
Quantum mechanics lab kit
,” <https://qubitekk.com/products/quantum-mechanics-lab-kit/>.
15.
Qutools
, “
Qued, a science kit for quantum physics
,” <https://qutools.com/qued/>.
16.
E. J.
Galvez
, “
Resource letter SPE-1: Single-photon experiments in the undergraduate laboratory
,”
Am. J. Phys.
82
,
1018
1028
(
2014
).
17.
E. J.
Galvez
, “
Photon quantum mechanics
,” <https://egalvez.colgate.domains/pql/>.
18.
P. G.
Kwiat
,
A. M.
Steinberg
, and
R. Y.
Chiao
, “
Observation of a ‘quantum eraser:’ A revival of coherence in a two-photon interference experiment
,”
Phys. Rev. A
45
,
7729
7739
(
1992
).
19.
E. J.
Galvez
, “
Qubit quantum mechanics with correlated-photon experiments
,”
Am. J. Phys.
78
,
510
519
(
2010
).
20.
R.
Werner
, “
Quantum states with Einstein-Podolsky-Rosen correlations admitting a hidden-variable model
,”
Phys. Rev. A
40
,
4277
4281
(
1989
).
21.
H.-P.
Breuer
and
F.
Petruccione
,
The Theory of Open Quantum Systems
(
Oxford U. P
.,
Oxford
,
2007
).
22.
A.
Salles
,
F.
de Melo
,
M. P.
Almeida
,
M.
Hor-Meyll
,
S. P.
Walborn
,
P. H.
Souto Ribeiro
, and
L.
Davidovich
, “
Experimental investigation of the dynamics of entanglement: Sudden death, complementarity, and continuous monitoring of the environment
,”
Phys. Rev. A
78
,
022322
(
2008
).
23.
E. J.
Galvez
, “
Remote quantum optics labs
,”
Proc. SPIE
11701
,
1170106
(
2021
).
24.
H.
Weinfurter
, “
Experimental Bell-state analysis
,”
Europhys. Lett.
25
(
8
),
559
564
(
1994
).
25.
S. L.
Braunstein
and
A.
Mann
, “
Measurement of the Bell operator and quantum teleportation
,”
Phys. Rev. A
51
,
R1727
R1730
(
1995
).
26.
S. P.
Walborn
,
A. N.
de Oliveira
,
S.
Pádua
, and
C. H.
Monken
, “
Multimode Hong-Ou-Mandel interference
,”
Phys. Rev. Lett.
90
,
143601
(
2003
).
27.
K.
Mattle
,
H.
Weinfurter
,
P. G.
Kwiat
, and
A.
Zeilinger
, “
Dense coding in experimental quantum communication
,”
Phys. Rev. Lett.
76
,
4656
4659
(
1996
).
28.
D.
Griffiths
,
Introduction to Quantum Mechanics
, 2nd. ed. (
Pearson Prentice Hall
,
New Jersey
,
2005
).
29.
E.
Knill
,
R.
Laflamme
, and
G. J.
Milburn
, “
A scheme for efficient quantum computation with linear optics
,”
Nature
409
,
46
52
(
2001
).
30.
X. Y.
Zou
,
L. J.
Wang
, and
L.
Mandel
, “
Induced coherence and indistinguishability in optical interference
,”
Phys. Rev. Lett.
67
,
318
321
(
1991
).
31.
Alpha
, “
Alpha's single photon detector initiative
,” <https://advlab.org/spqm/>.
32.
M.
Beck
, “
Coincidence counting units (ccus)
,” <http://people.reed.edu/∼beckm/qm/circuit/circuit.html>.
33.
M.
Mansuripur
and
E. M.
Wright
, “Fundamental properties of beamsplitters in classical and quantum optics,”
Am. J. Phys.
91
,
298
306
(
2023
).
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