We consider the quantum entanglement of the electronic and vibrational degrees of freedom in molecules with tendencies towards double welled potentials. In these bipartite systems, the von Neumann entropy of the reduced density matrix is used to quantify the electron-vibration entanglement for the lowest two vibronic wavefunctions obtained from a model Hamiltonian based on coupled harmonic diabatic potential-energy surfaces. Significant entanglement is found only in the region in which the ground vibronic state contains a density profile that is bimodal (i.e., contains two separate local maxima). However, in this region two distinct types of density and entanglement profiles are found: one type arises purely from the degeneracy of energy levels in the two potential wells and is destroyed by slight asymmetry, while the other arises through strong interactions between the diabatic levels of each well and is relatively insensitive to asymmetry. These two distinct types are termed fragile degeneracy-induced entanglement and persistent entanglement, respectively. Six classic molecular systems describable by two diabatic states are considered: ammonia, benzene, BNB, pyridine excited triplet states, the Creutz-Taube ion, and the radical cation of the “special pair” of chlorophylls involved in photosynthesis. These chemically diverse systems are all treated using the same general formalism and the nature of the entanglement that they embody is elucidated.

1.
J.
Horiuti
and
M.
Polanyi
,
J. Mol. Catal. A
199
,
185
(
2003
);
J.
Horiuti
and
M.
Polanyi
,
Transl. Acta Physicochim. URSS
2
,
505
(
1935
).
2.
3.
R. A.
Marcus
,
Trans. N. Y. Acad. Sci.
19
,
423
(
1957
).
4.
N. S.
Hush
,
J. Chem. Phys.
28
,
962
(
1958
).
5.
R. A.
Marcus
,
Discuss. Faraday Soc.
21
(
1960
).
6.
N. S.
Hush
,
Trans. Faraday Soc.
57
,
577
(
1961
).
7.
R. A.
Marcus
and
N.
Sutin
,
Biochim. Biophys. Acta
811
,
265
(
1985
).
8.
Electron Transfer in Biology and the Solid State
, Edited by
M. K.
Johnson
,
R. B.
King
,
J.
Donald
,
M.
Kurtz
,
Charles
Kutal
,
M. L.
Norton
, and
R. A.
Scott
(
American Chemical Society
,
Washington DC
,
1989
).
9.
Electron and Ion Transfer in Condensed Media
, edited by
A. A.
Kornyshev
,
M.
Tosi
and
J.
Ulstrup
, Ed. (
World Scientific
,
Singapore
,
1997
).
10.
Electron Transfer Reactions
Edited by
S.
Isied
(
American Chemical Society
,
Washington DC
,
1997
).
11.
Electron Transfer in Chemistry and Biology
, edited by
A.
Kutnetsov
and
J.
Ulstrup
(
Wiley
,
Hoboken NJ
,
1999
).
12.
Electron Transfer in Chemistry. Principles, Theories, Methods and Techniques
, edited by
V.
Balzani
(
Wiley-VCH
,
Hoboken NJ
,
2001
).
13.
14.
D. M.
Guldi
,
Chem. Soc. Rev.
31
,
22
(
2002
).
15.
T. W.
Marin
,
B. J.
Homoelle
,
K. G.
Spears
,
J. T.
Hupp
, and
L. O.
Spreer
,
J. Phys. Chem. A
106
,
1131
(
2002
).
16.
E. A.
Plummer
and
J. I.
Zink
,
Inorg. Chem.
45
,
6556
(
2006
).
17.
S. F.
Nelsen
,
Adv. Phys. Org. Chem.
41
,
183
(
2006
).
18.
V.
Coropceanu
,
J.
Cornil
,
D. A.
da Silva Filho
,
Y.
Olivier
,
R.
Silbey
, and
J. L.
Brédas
,
Chem. Rev.
107
,
926
(
2007
).
19.
20.
J.
Trost
and
K.
Hornberger
,
Phys. Rev. Lett.
103
,
023202
(
2009
).
21.
L.
Ziegler
and
A.
Albrecht
,
J. Chem. Phys.
60
,
3558
(
1974
).
22.
G.
Fischer
,
J. R.
Reimers
, and
I. G.
Ross
,
Chem. Phys.
62
,
187
(
1981
).
23.
H.
Köuppel
,
W.
Domcke
, and
L. S.
Cederbaum
,
Adv. Chem. Phys.
57
,
59
(
2007
).
24.
R.
Englman
,
The Jahn-Teller Effect in Molecules and Crystals
(
Wiley
,
New York
,
1972
).
25.
G.
Fischer
,
Vibronic Coupling
(
Academic
,
London
,
1984
).
26.
I. B.
Bersuker
,
Chem. Rev.
101
,
1067
(
2001
).
27.
M. A.
Neilsen
and
I. L.
Chuang
,
Quantum Computation and Quantum Information
(
Cambridge University Press
,
Cambridge
,
2000
).
28.
T. J.
Osborne
,
Phys. Rev. A
72
,
022309
(
2005
).
29.
X. W.
Hou
,
J. H.
Chen
, and
B.
Hu
,
Phys. Rev. A
71
,
034302
(
2005
).
30.
R.
Horodecki
,
P.
Horodecki
,
M.
Horodecki
, and
K.
Horodecki
,
Rev. Mod. Phys.
81
,
865
(
2009
).
31.
A. P.
Hines
,
C. M.
Dawson
,
R. H.
McKenzie
, and
G. J.
Milburn
,
Phys. Rev. A
70
,
022303
(
2004
).
32.
J. F.
Stanton
,
J. Chem. Phys.
133
,
174309
(
2010
).
34.
C.
Creutz
and
H.
Taube
,
J. Am. Chem. Soc.
91
,
3988
(
1969
).
35.
J. R.
Reimers
,
B. B.
Wallace
, and
N. S.
Hush
,
Philos. Trans. R. Soc. A
366
,
15
(
2008
).
36.
J. M.
Warman
,
M. P. d.
Haas
,
M. N.
Paddon-Row
,
E.
Cotsaris
,
N. S.
Hush
,
H.
Oevering
, and
J. W.
Verhoeven
,
Nature (London)
320
,
615
(
1986
).
37.
M. B.
Robin
and
P.
Day
,
Adv. Inorg. Chem. Radiochem.
10
,
247
(
1967
).
38.
P.
Day
,
N. S.
Hush
, and
R. J. H.
Clark
,
Philos. Trans. R. Soc. A
366
,
5
(
2008
).
39.
Z.-L.
Cai
and
J. R.
Reimers
,
J. Phys. Chem. A
104
,
8389
(
2000
).
40.
J. R.
Reimers
and
N. S.
Hush
,
J. Chem. Phys.
119
,
3262
(
2003
).
41.
N. S.
Hush
,
Prog. Inorg. Chem.
8
,
391
(
1967
).
42.
43.
C. P.
Meaney
,
T.
Duty
,
R. H.
McKenzie
, and
G. J.
Milburn
,
Phys. Rev. A
81
,
043805
(
2010
).
44.
J.
He
,
L.
Ye
, and
Z.-x.
Ni
,
Liangzi Dianzi Xuebao
24
,
579
(
2007
).
45.
H.-Q.
Fan
,
W.-L.
Yang
,
X.-R.
Huang
, and
M.
Feng
,
Chin. Phys. B
18
,
4893
(
2009
).
46.
Y.-Q.
Zhang
and
S.
Zhang
,
Chin. Phys. B
18
,
4683
(
2009
).
47.
T.
Niemczyk
,
F.
Deppe
,
H.
Huebl
,
E. P.
Menzel
,
F.
Hocke
,
M. J.
Schwarz
,
J. J.
Garcia-Ripoll
,
D.
Zueco
,
T.
Hümmer
,
E.
Solano
,
A.
Marx
, and
R.
Gross
,
Nat. Phys.
6
,
772
(
2010
).
48.
N. V.
Cohan
and
C. A.
Coulson
,
Trans. Faraday Soc.
52
,
1163
(
1956
).
49.
B. M.
Gimarc
,
J. Am. Chem. Soc.
93
,
593
(
1971
).
50.
I. B.
Bersuker
,
N. N.
Gorinchoi
, and
V. Z.
Polinger
,
Theor. Chim. Acta
66
,
161
(
1984
).
51.
D. M.
Friedrich
and
W. M.
McClain
,
Chem. Phys. Lett.
32
,
541
(
1975
).
52.
N.
Mikami
and
M.
Ito
,
J. Chem. Phys.
64
,
3077
(
1976
).
53.
R. P.
Rava
,
L.
Goodman
, and
K.
Krogh-Jespersen
,
J. Chem. Phys.
74
,
273
(
1981
).
54.
N.
Mikami
and
M.
Ito
,
Chem. Phys.
23
,
141
(
1977
).
55.
L.
Blancafort
and
M.
Sola
,
J. Phys. Chem. A
110
,
11219
(
2006
).
56.
See supplementary material at http://dx.doi.org/10.1063/1.3671386 for the derivation of Eq. (15) and a description of the 3-state and 5-state extended vibronic coupling models for closed-shell reactions, their reduction to effective 2-state models, parameter determinations for ammonia and benzene based on experimental data, and the differences between the entanglements manifest by the full models and their effective 2-state approximations.
57.
M.
Gouterman
,
J. Chem. Phys.
42
,
351
(
1965
).
58.
M.
Born
and
R.
Oppenheimer
,
Ann. Phys.
84
,
457
(
1927
).
59.
G.
Liberti
,
R. L.
Zaffino
,
F.
Piperno
, and
F.
Plastina
,
Phys. Rev. A
73
,
032346
(
2006
).
60.
M. J.
Bremner
,
C. M.
Dawson
,
J. L.
Dodd
,
A.
Gilchrist
,
A. W.
Harrow
,
D.
Mortimer
,
M. A.
Nielsen
, and
T. J.
Osborne
,
Phys. Rev. Lett.
89
,
247902
(
2002
).
61.
E.
Knill
,
Nature (London)
434
,
39
(
2005
).
62.
A. J.
Ferguson
,
P. A.
Cain
,
D. A.
Williams
, and
G. A. D.
Briggs
,
Phys. Rev. A
65
,
034303
(
2002
).
63.
S. Y.
Cho
and
R. H.
McKenzie
,
Phys. Rev. A
73
,
012109
(
2006
).
64.
R.
Englman
and
T.
Vértesi
,
J. Chem. Phys.
125
,
064102
(
2006
).
66.
T.
Vértesi
and
R.
Englman
,
Phys. Rev. A
75
,
022315
(
2007
).
67.
D. Wahyu
Utami
and
A. A.
Clerk
,
Phys. Rev. A
78
,
042323
(
2008
).
68.
E. B. D.
Wilson
,
J. C.
Cross
, and
C.
Paul
,
Molecular Vibrations: The Theory of Infrared and Raman Vibrational Spectra
(
McGraw-Hill
,
New York
,
1955
).
69.
J. R.
Reimers
and
N. S.
Hush
,
Chem. Phys.
299
,
79
(
2004
).
70.
K. D.
Demadis
,
C. M.
Hartshorn
, and
T. J.
Meyer
,
Chem. Rev.
101
,
2655
(
2001
).
71.
H. A.
Jahn
and
E.
Teller
,
Proc. R. Soc. A
161
,
220
(
1937
).
72.
I. B.
Bersuker
,
The Jahn-Teller Effect and Vibronic Interactions in Modern Chemistry
(
Springer
,
New York
,
1984
)
73.
T. A.
Costi
and
R. H.
McKenzie
,
Phys. Rev. A
68
,
034301
(
2003
).
74.
A.
Kopp
and
K. Le
Hur
,
Phys. Rev. Lett.
98
,
220401
(
2007
).
75.
S.
Paganelli
and
S.
Ciuchi
,
J. Phys.: Condens. Matter
18
,
7669
(
2006
).
76.
S.
Paganelli
and
S.
Ciuchi
,
J. Phys.: Condens. Matter
20
,
235203
(
2008
).
77.
M.
Reis
,
M. O. T.
Cunha
,
A. C.
Oliveira
, and
M. C.
Nemes
,
Phys. Lett. A
344
,
164
(
2005
).
78.
N.
Lambert
,
C.
Emary
, and
T.
Brandes
,
Phys. Rev. Lett.
92
,
073602
(
2004
).
79.
G.
Levine
and
V. N.
Muthukumar
,
Phys. Rev. B
69
,
113203
(
2004
).
80.
C.
Emary
,
N.
Lambert
, and
T.
Brandes
,
Phys. Rev. A
71
,
062302
(
2005
).
81.
M. C.
Nemes
,
K.
Furuya
,
G. Q.
Pellegrino
,
A. C.
Oliveira
,
M.
Reis
, and
L.
Sanz
,
Phys. Lett. A
354
,
60
(
2006
).
82.
Q.
Xie
and
W.
Hai
,
Eur. Phys. J. D
39
,
277
(
2006
).
83.
T.
Moreira
,
G. Q.
Pellegrino
,
J. G.
Peixoto De Faria
,
M. C.
Nemes
,
F.
Camargo
, and
A. F. R.
de Toledo Piza
,
Phys. Rev. E
77
,
051102
(
2008
).
84.
Y.
Liu
,
Y.
Zheng
,
W.
Ren
, and
S.
Ding
,
Phys. Rev. A
78
,
032523
(
2008
).
85.
M. S.
Santhanam
,
V. B.
Sheorey
, and
A.
Lakshminarayan
,
Phys. Rev. E
77
,
026213
(
2008
).
86.
A.
Bermudez
,
M. A.
Martin-Delgado
, and
A.
Luis
,
Phys. Rev. A
77
,
063815
(
2008
).
87.
E. A.
Chagas
and
K.
Furuya
,
Phys. Lett. A
372
,
5564
(
2008
).
88.
X. W.
Hou
,
M. F.
Wan
, and
Z. Q.
Ma
,
Phys. Rev. A
79
,
022308
(
2009
).
89.
X. W.
Hou
,
J. H.
Chen
,
M. F.
Wan
, and
Z. Q.
Ma
,
J. Phys. A
42
,
075301
(
2009
).
90.
Q.
Wang
,
A.-Y.
Hu
, and
H.
Zheng
,
Phys. Rev. B
80
,
214301
(
2009
).
91.
M.-J.
Hwang
and
M.-S.
Choi
,
Phys. Rev. A
82
,
025802
(
2010
).
92.
A.
Einstein
,
B.
Podolsky
, and
N.
Rosen
,
Phys. Rev.
47
,
777
(
1935
).
93.
D.
Bohm
,
Quantum Theory
(
Prentice-Hall
,
Englewood Cliffs, NJ
,
1951
).
94.
D.
Bohm
and
Y.
Aharonov
,
Phys. Rev.
108
,
1070
(
1957
).
95.
P.-O.
Löwdin
,
Phys. Rev.
97
,
1509
(
1955
).
96.
P. H.
Citrin
,
J. Am. Chem. Soc.
95
,
6472
(
1973
).
97.
J.
Swalen
and
J.
Ibers
,
J. Chem. Phys.
36
,
1914
(
1962
).
98.
P. H.
Cribb
,
S.
Nordholm
, and
N. S.
Hush
,
Chem. Phys.
29
,
43
(
1978
).
99.
P. H.
Cribb
,
S.
Nordholm
, and
N. S.
Hush
,
Chem. Phys.
29
,
31
(
1978
).
100.
P. H.
Cribb
,
S.
Nordholm
, and
N. S.
Hush
,
Chem. Phys.
44
,
315
(
1979
).
101.
J. R.
Reimers
and
N. S.
Hush
,
Chem. Phys.
134
,
323
(
1989
).
102.
A. G.
Ozkabak
,
L.
Goodman
, and
K. B.
Wiberg
,
J. Chem. Phys.
92
,
4115
(
1990
).
103.
J.
Murakami
,
K.
Kaya
, and
M.
Ito
,
J. Chem. Phys.
72
,
3263
(
1980
).
104.
J. R.
Reimers
,
W. A.
Shapley
,
A. P.
Rendell
, and
N. S.
Hush
,
J. Chem. Phys.
119
,
3249
(
2003
).

Supplementary Material

You do not currently have access to this content.