Observing the Progressive Decoherence of the “Meter” in a Quantum Measurement

M. Brune; E. Hagley; J. Dreyer; X. Maître; A. Maali; C. Wunderlich; J. M. Raimond; S. Haroche

doi:10.1103/PhysRevLett.77.4887

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Observing the Progressive Decoherence of the “Meter” in a Quantum Measurement

M. Brune, E. Hagley, J. Dreyer, X. Maître, A. Maali, C. Wunderlich, J. M. Raimond, and S. Haroche

Laboratoire Kastler Brossel, Département de Physique de l'Ecole Normale Supérieure, 24 Rue Lhomond, F-75231 Paris Cedex 05, France

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Phys. Rev. Lett. 77, 4887 – Published 9 December, 1996

DOI: https://doi.org/10.1103/PhysRevLett.77.4887

Abstract

A mesoscopic superposition of quantum states involving radiation fields with classically distinct phases was created and its progressive decoherence observed. The experiment involved Rydberg atoms interacting one at a time with a few photon coherent field trapped in a high $Q$ microwave cavity. The mesoscopic superposition was the equivalent of an “ $atom + measuring apparatus$ ” system in which the “meter” was pointing simultaneously towards two different directions—a “Schrödinger cat.” The decoherence phenomenon transforming this superposition into a statistical mixture was observed while it unfolded, providing a direct insight into a process at the heart of quantum measurement.

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Published 12 October, 2012

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References (21)

J. A. Wheeler and W. H. Zurek, Quantum Theory of Measurement (Princeton Univ. Press, Princeton, NJ, 1983).
E. Schrödinger, Naturwissenschaften 23, 807, 823, 844 (1935); reprinted in English in [[1]].
J. von Neumann, in Matematische Grundlagen der Quantenmechanik (Springer, Berlin, 1932); reprinted in English in [[1]].
W. H. Zurek, Phys. Today 44, No. 10, 36 (1991).
W. H. Zurek, A. O. Caldeira and A. J. Leggett, E. Joos and H. D. Zeh, R. OmnèsPhys. Rev. D 24, 1516 (1981); 26, 1862 (1982); Physica (Amsterdam) 121A, 587 (1983); Z. Phys. B 59, 223 (1985); , The Interpretation of Quantum Mechanics (Princeton University Press, Princeton, NJ, 1994).
R. J. Glauber, Phys. Rev. 131, 2766 (1963).
D. F. Waals and G. J. Milburn, Phys. Rev. A 31, 2403 (1985).
M. Brune et al., Phys. Rev. A 45, 5193 (1992).
C. Monroe et al., Science 272, 1131 (1996).
B. Yurke and D. Stoler, Phys. Rev. Lett. 57, 13 (1986) B. Yurke et al., Phys. Rev. A 42, 1703 (1990) G. Milburn, ibid. 33, 674 (1986) V. Buzek et al., Phys. Rev. A 45, 8190 (1992).
C. N. Savage et al., Opt. Lett. 15, 628 (1990).
R. G. Hulet and D. Kleppner, Phys. Rev. Lett. 51, 1430 (1983).
S. Haroche and J. M. Raimond, in Cavity Quantum Electrodynamics, P. Berman (Academic Press, New York, 1994), p. 123.
M. Brune et al., Phys. Rev. Lett. 76, 1800 (1996).
P. Nussenzveig et al., Phys. Rev. A 48, 3991 (1993).
N. F. Ramsey, Molecular Beams (Oxford Univ. Press, New York, 1985).
M. O. Scully et al., Nature (London) 351, 111 (1991) S. Haroche et al., Appl. Phys. B 54, 355 (1992).
T. Pfau et al., Phys. Rev. Lett. 73, 1223 (1994) M. S. Chapman et al., 75, 3783 (1995).
M. Brune et al., Phys. Rev. Lett. 72, 3339 (1994).
L. Davidovich et al., Phys. Rev. A 53, 1295 (1996).
The calculation— to be published—generalizes to arbitrary $φ$ values the derivation of [[20]], which was restricted to $φ = π / 2$ . It describes independently atom-field interaction and relaxation and neglects fluctuations of atomic velocity as well as of atom number (possibility of two atoms in each preparation pulse).

[c1] J. A. Wheeler and W. H. Zurek, Quantum Theory of Measurement (Princeton Univ. Press, Princeton, NJ, 1983).

[c2] E. Schrödinger, Naturwissenschaften 23, 807, 823, 844 (1935); reprinted in English in [[1]].

[c3] J. von Neumann, in Matematische Grundlagen der Quantenmechanik (Springer, Berlin, 1932); reprinted in English in [[1]].

[c4] W. H. Zurek, Phys. Today 44, No. 10, 36 (1991).

[c5] W. H. Zurek, A. O. Caldeira and A. J. Leggett, E. Joos and H. D. Zeh, R. OmnèsPhys. Rev. D 24, 1516 (1981); 26, 1862 (1982); Physica (Amsterdam) 121A, 587 (1983); Z. Phys. B 59, 223 (1985); , The Interpretation of Quantum Mechanics (Princeton University Press, Princeton, NJ, 1994).

[c6] R. J. Glauber, Phys. Rev. 131, 2766 (1963).

[c7] D. F. Waals and G. J. Milburn, Phys. Rev. A 31, 2403 (1985).

[c8] M. Brune et al., Phys. Rev. A 45, 5193 (1992).

[c9] C. Monroe et al., Science 272, 1131 (1996).

[c10] B. Yurke and D. Stoler, Phys. Rev. Lett. 57, 13 (1986) B. Yurke et al., Phys. Rev. A 42, 1703 (1990) G. Milburn, ibid. 33, 674 (1986) V. Buzek et al., Phys. Rev. A 45, 8190 (1992).

[c11] C. N. Savage et al., Opt. Lett. 15, 628 (1990).

[c12] R. G. Hulet and D. Kleppner, Phys. Rev. Lett. 51, 1430 (1983).

[c13] S. Haroche and J. M. Raimond, in Cavity Quantum Electrodynamics, P. Berman (Academic Press, New York, 1994), p. 123.

[c14] M. Brune et al., Phys. Rev. Lett. 76, 1800 (1996).

[c15] P. Nussenzveig et al., Phys. Rev. A 48, 3991 (1993).

[c16] N. F. Ramsey, Molecular Beams (Oxford Univ. Press, New York, 1985).

[c17] M. O. Scully et al., Nature (London) 351, 111 (1991) S. Haroche et al., Appl. Phys. B 54, 355 (1992).

[c18] T. Pfau et al., Phys. Rev. Lett. 73, 1223 (1994) M. S. Chapman et al., 75, 3783 (1995).

[c19] M. Brune et al., Phys. Rev. Lett. 72, 3339 (1994).

[c20] L. Davidovich et al., Phys. Rev. A 53, 1295 (1996).

[c21] The calculation— to be published—generalizes to arbitrary $φ$ values the derivation of [[20]], which was restricted to $φ = π / 2$ . It describes independently atom-field interaction and relaxation and neglects fluctuations of atomic velocity as well as of atom number (possibility of two atoms in each preparation pulse).

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Observing the Progressive Decoherence of the “Meter” in a Quantum Measurement

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Nobel Prize—Tools for Quantum Tinkering

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