Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

Observation of incoherent relaxation by tunneling in a macroscopic two-state system

Siyuan Han, J. Lapointe, James E. Lukens

Published Feb 11, 1991• 70 citations
Publisher

Abstract

The dynamics of a dissipative, quantized macroscopic two-state system have been experimentally investigated through the measurement of tunneling transitions between the adjacent, equal-energy fluxoid states of a superconducting loop containing Josephson junctions. The tunneling rate \ensuremath{\Gamma} has been observed to approach zero as a power law in the temperature, giving a damping parameter \ensuremath{\alpha}=1.44, in the incoherent relaxation regime. The predicted exponential dependence of \ensuremath{\Gamma} on barrier height has been quantitatively confirmed.

DOI
10.1103/physrevlett.66.810

Related papers

Quantum Mechanics of a Macroscopic Variable: The Phase Difference of a Josephson Junction

John L. Clarke, Andrew N. Cleland, Michel Devoret +2 more

Experiments to investigate the quantum behavior of a macroscopic degree of freedom, namely the phase difference across a Josephson tunnel junction, are described. The experiments involve measurements of the escape rate of the junction from its zero voltage state. Low temperature measurements of the escape rate for junctions that are either nearly undamped or moderately damped agree very closely with predictions for macroscopic quantum tunneling, with no adjustable parameters. Microwave spectroscopy reveals quantized energy levels in the potential well of the junction in excellent agreement with quantum-mechanical calculations. The system can be regarded as a "macroscopic nucleus with wires."

Science•Feb 26, 1988•359 citations

Time-Resolved Measurement of Dissipation-Induced Decoherence in a Josephson Junction

Siyuan Han, Yang Yu, Xi Chu +2 more

We determined the dissipation-induced decoherence time (DIDT) of a superconducting Josephson tunnel junction by time-resolved measurements of its escape dynamics. Double-exponential behavior of the time-dependent escape probability was observed, suggesting the occurrence of a two-level decay-tunneling process in which energy relaxation from the excited to the ground level significantly affects the escape dynamics of the system. The observation of temporal double-exponential dependence enables direct measurements of the DIDT, a property critical to the study of quantum dynamics and the realization of macroscopic quantum coherence and quantum computing. We found that the DIDT was tau(d) > 11 micros at T = 0.55 K, demonstrating good prospects for implementing quantum computing with Josephson devices.

Science•Aug 24, 2001•103 citations

Macroscopic quantum effects in a Josephson tunnel junction

J. R. Clarke, A.N. Cleland, Michel Devoret +2 more

This paper discusses the observation of quantum effects in the macroscopic system of a Josephson tunnel junction. The macroscopic degree of freedom is the phase difference delta between the phases of the order parameters in the two superconductors on either side of the tunnel barrier. As we shall see, the anharmonicity enables us to observe the quantized energy levels because they are no longer equally spaced, and to observe the zero point motion by the demonstration that the system tunnels out of its initial state. 6 refs., (LSP)

•May 1, 1987•0 citations

Photoinduced macroscopic quantum tunneling

Sudip Chakravarty, Steven Allan Kivelson

Recently there has been interest in macroscopic systems which can be described in terms of the quantum dynamics of the same collective variables which describe their classical behavior. In particular, there has been considerable interest in the following questions: (1) Is it possible to observe unambiguous evidence of the quantum-mechanical nature of a macroscopic collective coordinate? (2) In what way is the quantum mechanics of a macroscopic variable different from that of a microscopic variable or, in other words, what is the effect of dissipation on the dynamics of a quantum-mechanical system? Spectroscopic evidence of the quantization of energy levels can be found by measuring the system's response to an applied ac perturbation, exploiting the quantum-mechanical relation between energy and frequency. The specific system studied is a superconducting quantum interference device (SQUID). It is shown that a time-varying magnetic field through the superconducting loop in a rf SQUID can cause transitions between different fluxoid states. The role of dissipation is discussed in detail, and it is shown that in the case that dissipation is characterized by linear damping in the classical limit, the photon-absorption process depends critically on the ratio of the resistance of the weak link to the fundamental unit of resistance h/${e}^{2}$. .AE

Physical review. B, Condensed matter•Jul 1, 1985•46 citations

Quantitative Study of the Effect of the Environment on Macroscopic Quantum Tunneling

D. B. Schwartz, B. Sen, Charles N. Archie +1 more

Data are presented on the temperature-dependent escape rates of a macroscopic system, a SQUID containing a highly damped Josephson junction, from its metastable state. These data provide the first quantitative confirmation of recent predictions of the exponential effects of temperature and damping on quantum tunneling in macroscopic systems in contrast to previously reported discrepancies. Predicted quantum corrections to thermally activated escape at high temperatures are not observed.

Physical Review Letters•Oct 7, 1985•172 citations

Resonant enhancement of MQT in Josephson junctions: the influence of coherent two-level systems

M. V. Fistul

We report a theoretical study of the macroscopic quantum tunneling (MQT) in small Josephson junctions containing randomly distributed two-level systems. We focus on the magnetic field dependent crossover temperature $T_{cr}$ between the thermal fluctuation and quantum regimes of switching from the superconducting (the zero-voltage) state to a resistive one. In the absence of two-levels systems the crossover temperature shows a smooth decrease with an applied magnetic field characterized by an external flux $Φ$. Beyond that we predict a narrow peak in the dependence of $T_{cr}(Φ)$ occurring in the intermediate range of $Φ$. The effect becomes more pronounced as the junction size increases. We explain this effect quantitatively by a strong resonant suppression of a potential barrier for the Josephson phase escape that is due to the coherent quantum Rabi oscillations in two-level systems present in the junction.

arXiv:1410.4388•Oct 16, 2014•0 citations
The dynamics of a dissipative, quantized macroscopic two-state system have been experimentally investigated through the measurement of tunneling transitions between the adjacent, equal-energy fluxoid states of a superconducting loop containing Josephson junctions. The tunneling rate \ensuremath{\Gamma} has been observed to approach zero as a power law in the temperature, giving a damping parameter \ensuremath{\alpha}=1.44, in the incoherent relaxation regime. The predicted exponential dependence of \ensuremath{\Gamma} on barrier height has been quantitatively confirmed.
Experiments to investigate the quantum behavior of a macroscopic degree of freedom, namely the phase difference across a Josephson tunnel junction, are described. The experiments involve measurements of the escape rate of the junction from its zero voltage state. Low temperature measurements of the escape rate for junctions that are either nearly undamped or moderately damped agree very closely with predictions for macroscopic quantum tunneling, with no adjustable parameters. Microwave spectroscopy reveals quantized energy levels in the potential well of the junction in excellent agreement with quantum-mechanical calculations. The system can be regarded as a "macroscopic nucleus with wires."
We determined the dissipation-induced decoherence time (DIDT) of a superconducting Josephson tunnel junction by time-resolved measurements of its escape dynamics. Double-exponential behavior of the time-dependent escape probability was observed, suggesting the occurrence of a two-level decay-tunneling process in which energy relaxation from the excited to the ground level significantly affects the escape dynamics of the system. The observation of temporal double-exponential dependence enables direct measurements of the DIDT, a property critical to the study of quantum dynamics and the realization of macroscopic quantum coherence and quantum computing. We found that the DIDT was tau(d) > 11 micros at T = 0.55 K, demonstrating good prospects for implementing quantum computing with Josephson devices.
This paper discusses the observation of quantum effects in the macroscopic system of a Josephson tunnel junction. The macroscopic degree of freedom is the phase difference delta between the phases of the order parameters in the two superconductors on either side of the tunnel barrier. As we shall see, the anharmonicity enables us to observe the quantized energy levels because they are no longer equally spaced, and to observe the zero point motion by the demonstration that the system tunnels out of its initial state. 6 refs., (LSP)
Recently there has been interest in macroscopic systems which can be described in terms of the quantum dynamics of the same collective variables which describe their classical behavior. In particular, there has been considerable interest in the following questions: (1) Is it possible to observe unambiguous evidence of the quantum-mechanical nature of a macroscopic collective coordinate? (2) In what way is the quantum mechanics of a macroscopic variable different from that of a microscopic variable or, in other words, what is the effect of dissipation on the dynamics of a quantum-mechanical system? Spectroscopic evidence of the quantization of energy levels can be found by measuring the system's response to an applied ac perturbation, exploiting the quantum-mechanical relation between energy and frequency. The specific system studied is a superconducting quantum interference device (SQUID). It is shown that a time-varying magnetic field through the superconducting loop in a rf SQUID can cause transitions between different fluxoid states. The role of dissipation is discussed in detail, and it is shown that in the case that dissipation is characterized by linear damping in the classical limit, the photon-absorption process depends critically on the ratio of the resistance of the weak link to the fundamental unit of resistance h/e2{e}^{2}e2. .AE
We report a theoretical study of the macroscopic quantum tunneling (MQT) in small Josephson junctions containing randomly distributed two-level systems. We focus on the magnetic field dependent crossover temperature TcrT_{cr}Tcr​ between the thermal fluctuation and quantum regimes of switching from the superconducting (the zero-voltage) state to a resistive one. In the absence of two-levels systems the crossover temperature shows a smooth decrease with an applied magnetic field characterized by an external flux ΦΦΦ. Beyond that we predict a narrow peak in the dependence of Tcr(Φ)T_{cr}(Φ)Tcr​(Φ) occurring in the intermediate range of ΦΦΦ. The effect becomes more pronounced as the junction size increases. We explain this effect quantitatively by a strong resonant suppression of a potential barrier for the Josephson phase escape that is due to the coherent quantum Rabi oscillations in two-level systems present in the junction.