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

arXiv:1109.4027 · Physical Review B

Decoherence and the retrieval of lost information

Yin Ye, Yunshan Cao, Xin-Qi Li, S. A. Gurvitz

Published Dec 15, 2011• 4 citations
arXivHTMLPDF

Abstract

We show that, contrary to common prejudice, a measurement of an open quantum system can reduce its decoherence rate. We demonstrate this in an example of indirect measurement of a qubit, where information regarding its state is hidden in the environment. This information is extracted by a distant device, coupled with the environment only. We also show that the reduction of decoherence generated by this device is accompanied by diminution of the environmental noise in the vicinity of the qubit. An interpretation of these results in terms of quantum interference on large scales is presented.

DOI
10.1103/physrevb.84.245311

Related papers

Aspects of decoherence in qubit systems

Cox, Timothy

We present a theoretical discussion of various aspects of the dynamics of information in quantum systems of qubits. We begin by reviewing ideas about entanglement and information in systems of qubits, different models for realistic qubits coupled to an external environment, how this causes the loss of information stored in qubits, and some practical designs for qubits that have been created. Then we study how the state of many-body systems can be decomposed in terms of its different subsystems and derived a hierarchy of equations describing the motion of these different parts. We show that in a qubit system, the central objects in this hierarchy are correlators between different components of different qubits. Systems where the environment coupled to a central qubit is a "spin bath'' of environmental qubits are then considered in detail and we find that information lost by the central qubit is transferred via a cascade to higher and higher order correlations with the environment. We discuses this process in the realistic example of an "Fe₈'' magnetic molecule qubit. Finally we discuss simple models of the dynamics of many entangled qubits.

•Jan 1, 2019•0 citations

Decoherence of Quantum Signals

Mariam Janelidze, Marina Alekseevna Kurdadze

Decoherence of quantum signals is one of the main challenges of modern quantum information systems and technologies. This phenomenon is defined as the degradation of the coherent state of a quantum system as a result of environmental influences, which directly affects the information reliability of qubits, as well as the preservation of oscillations and superposition. Decoherence is a natural process of a quantum system when the system interacts with a thermally active or other quantum-mechanically active environment. This effect is important both in theoretical research and in practical quantum devices, including the development of quantum telecommunications, quantum computing, and high-precision quantum sensors. In cryogenic environments, where the temperature approaches zero Kelvin, the reduction of thermal excitations ensures the long-term preservation of the quantum signal. Under such conditions, zero-point fluctuations remain the only source of decoherence, which significantly increases the coherence of qubits and the possibility of performing complex quantum operations. At relatively high temperatures, bosonic and color spectrum excitations significantly increase the decoherence rate, which leads to rapid degradation of the quantum signal and a rapid transition of the system state towards the classical paradigm.

Works of Georgian Technical University•Jun 22, 2026•0 citations

Decoherence

Mikio Nakahara

A quantum system is always in interaction with its environment. This interaction inevitably alters the state of the quantum system, which causes loss of information encoded in the system. The system under consideration is not a closed system any more when interaction with the outside world is in action. We formulate the theory of an open quantum system in this chapter by regarding the combined system of the quantum system and its environment as a closed system and subsequently trace out the environmental degrees of freedom. Let ρS and ρE be the density matrices of the system and the environment, respectively. Even when the initial state is an uncorrelated state ρS ⊗ ρE , the system-environment interaction entangles the total system so that the total state develops to an inseparable entangled state in general. Decoherence is a process in which environment causes various changes in the quantum system, which manifests itself as undesirable noise.

CRC Press eBooks•Mar 11, 2008•0 citations

FEEDBACK IN OPEN QUANTUM SYSTEMS

Howard M. Wiseman

Open quantum systems continually lose information to their surroundings. In some cases this information can be readily retrieved from the environment and put to good use by engineering a feedback loop to control the system dynamics. Two cases are distinguished: one where the feedback mechanism involves a measurement of the environment, and the other where no measurement is made. It is shown that the latter case can always replicate the former, but not vice versa. This emphasizes the quantum nature of the information being fed back. Two approaches are used to describe the feedback: quantum trajectories (which apply only for feedback based on measurement) and quantum Langevin equations (which can be used in either case), and the results are shown to be equivalent. The obvious applications for the theory are in quantum optics, where the information is lost by radiation damping and can be retrieved by photodetection. A few examples are discussed, one of which is particularly interesting as it has no classical counterpart.

Modern Physics Letters B•May 20, 1995•9 citations

Decoherence in large quantum registers under variable interaction with the environment

Marko Lovrić, Hans Georg Krojanski, Dieter Suter

Effective quantum-information processing requires coherent control of large numbers of qubits on a time scale that is short compared to the decoherence time of the system. It is therefore important to extrapolate and measure decoherence times for large quantum registers and to determine the effect of different couplings between system and environment on the decoherence rate. For this purpose, we have experimentally realized a system that allows one to generate model quantum registers with more than 100 qubits and measure the decay of the information in these states while adjusting the strength of the interaction between the quantum register and the environment. Our results indicate a power-law dependence of the decoherence rate on the number of qubits in the system, with an exponent of the order of 0.5. This behavior remains qualitatively unchanged when the coupling strength to the environment is reduced by about an order of magnitude.

Physical Review A•Apr 3, 2007•65 citations

Measurement-induced quantum coherence recovery

Jin‐Shi Xu, Chuan‐Feng Li, Xu‐Bo Zou +4 more

We show that measurement can recover the quantum coherence of a qubit in a pure dephasing environment. The experimental demonstration of this in an optical system by comparing the visibilities (and fidelities) of the final states with and without measurement is provided here. This method can be extended to other two-level quantum systems and entangled states in a dephasing evolution environment. It may also be used to implement other types of quantum information processing.

arXiv:0810.5272•New Journal of Physics•Apr 3, 2009•7 citations
We show that, contrary to common prejudice, a measurement of an open quantum system can reduce its decoherence rate. We demonstrate this in an example of indirect measurement of a qubit, where information regarding its state is hidden in the environment. This information is extracted by a distant device, coupled with the environment only. We also show that the reduction of decoherence generated by this device is accompanied by diminution of the environmental noise in the vicinity of the qubit. An interpretation of these results in terms of quantum interference on large scales is presented.
We present a theoretical discussion of various aspects of the dynamics of information in quantum systems of qubits. We begin by reviewing ideas about entanglement and information in systems of qubits, different models for realistic qubits coupled to an external environment, how this causes the loss of information stored in qubits, and some practical designs for qubits that have been created. Then we study how the state of many-body systems can be decomposed in terms of its different subsystems and derived a hierarchy of equations describing the motion of these different parts. We show that in a qubit system, the central objects in this hierarchy are correlators between different components of different qubits. Systems where the environment coupled to a central qubit is a "spin bath'' of environmental qubits are then considered in detail and we find that information lost by the central qubit is transferred via a cascade to higher and higher order correlations with the environment. We discuses this process in the realistic example of an "Fe₈'' magnetic molecule qubit. Finally we discuss simple models of the dynamics of many entangled qubits.
Decoherence of quantum signals is one of the main challenges of modern quantum information systems and technologies. This phenomenon is defined as the degradation of the coherent state of a quantum system as a result of environmental influences, which directly affects the information reliability of qubits, as well as the preservation of oscillations and superposition. Decoherence is a natural process of a quantum system when the system interacts with a thermally active or other quantum-mechanically active environment. This effect is important both in theoretical research and in practical quantum devices, including the development of quantum telecommunications, quantum computing, and high-precision quantum sensors. In cryogenic environments, where the temperature approaches zero Kelvin, the reduction of thermal excitations ensures the long-term preservation of the quantum signal. Under such conditions, zero-point fluctuations remain the only source of decoherence, which significantly increases the coherence of qubits and the possibility of performing complex quantum operations. At relatively high temperatures, bosonic and color spectrum excitations significantly increase the decoherence rate, which leads to rapid degradation of the quantum signal and a rapid transition of the system state towards the classical paradigm.
A quantum system is always in interaction with its environment. This interaction inevitably alters the state of the quantum system, which causes loss of information encoded in the system. The system under consideration is not a closed system any more when interaction with the outside world is in action. We formulate the theory of an open quantum system in this chapter by regarding the combined system of the quantum system and its environment as a closed system and subsequently trace out the environmental degrees of freedom. Let ρS and ρE be the density matrices of the system and the environment, respectively. Even when the initial state is an uncorrelated state ρS ⊗ ρE , the system-environment interaction entangles the total system so that the total state develops to an inseparable entangled state in general. Decoherence is a process in which environment causes various changes in the quantum system, which manifests itself as undesirable noise.
Open quantum systems continually lose information to their surroundings. In some cases this information can be readily retrieved from the environment and put to good use by engineering a feedback loop to control the system dynamics. Two cases are distinguished: one where the feedback mechanism involves a measurement of the environment, and the other where no measurement is made. It is shown that the latter case can always replicate the former, but not vice versa. This emphasizes the quantum nature of the information being fed back. Two approaches are used to describe the feedback: quantum trajectories (which apply only for feedback based on measurement) and quantum Langevin equations (which can be used in either case), and the results are shown to be equivalent. The obvious applications for the theory are in quantum optics, where the information is lost by radiation damping and can be retrieved by photodetection. A few examples are discussed, one of which is particularly interesting as it has no classical counterpart.
Effective quantum-information processing requires coherent control of large numbers of qubits on a time scale that is short compared to the decoherence time of the system. It is therefore important to extrapolate and measure decoherence times for large quantum registers and to determine the effect of different couplings between system and environment on the decoherence rate. For this purpose, we have experimentally realized a system that allows one to generate model quantum registers with more than 100 qubits and measure the decay of the information in these states while adjusting the strength of the interaction between the quantum register and the environment. Our results indicate a power-law dependence of the decoherence rate on the number of qubits in the system, with an exponent of the order of 0.5. This behavior remains qualitatively unchanged when the coupling strength to the environment is reduced by about an order of magnitude.