scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Dynamics of decoherence without dissipation in a squeezed thermal bath

23 Oct 2007-Journal of Physics A (IOP Publishing)-Vol. 40, Iss: 45, pp 13735-13754
TL;DR: In this article, a generic open quantum system where the coupling between the system and its environment is of an energy-preserving quantum nondemolition (QND) type is studied.
Abstract: We study a generic open quantum system where the coupling between the system and its environment is of an energy-preserving quantum nondemolition (QND) type. We obtain the general master equation for the evolution of such a system under the influence of a squeezed thermal bath of harmonic oscillators. From the master equation it can be seen explicitly that the process involves decoherence or dephasing without any dissipation of energy. We work out the decoherence-causing term in the high- and zero-temperature limits and check that they match with known results for the case of a thermal bath. The decay of the coherence is quantified as well by the dynamics of the linear entropy of the system under various environmental conditions. We make a comparison of the quantum statistical properties between QND and dissipative types of evolution using a two-level atomic system and a harmonic oscillator.
Citations
More filters
Journal ArticleDOI
TL;DR: It is shown that a realistic controlled bidirectional remote state preparation is possible using a large class of entangled quantum states having a particular structure.
Abstract: It is shown that a realistic controlled bidirectional remote state preparation is possible using a large class of entangled quantum states having a particular structure. Existing protocols of probabilistic, deterministic and joint remote state preparation are generalized to obtain the corresponding protocols of controlled bidirectional remote state preparation (CBRSP). A general way of incorporating the effects of two well-known noise processes, the amplitude-damping and phase-damping noise, on the probabilistic CBRSP process is studied in detail by considering that noise only affects the travel qubits of the quantum channel used for the probabilistic CBRSP process. Also indicated is how to account for the effect of these noise channels on deterministic and joint remote state CBRSP protocols.

86 citations

Journal ArticleDOI
TL;DR: In this article, the effect of noise on various protocols of secure quantum communication has been studied and two protocols based on single-qubit states and two based on entangled states were compared.
Abstract: The effect of noise on various protocols of secure quantum communication has been studied. Specifically, we have investigated the effect of amplitude damping, phase damping, squeezed generalized amplitude damping, Pauli type as well as various collective noise models on the protocols of quantum key distribution, quantum key agreement, quantum secure direct quantum communication and quantum dialogue. From each type of protocol of secure quantum communication, we have chosen two protocols for our comparative study: one based on single-qubit states and the other one on entangled states. The comparative study reported here has revealed that single-qubit-based schemes are generally found to perform better in the presence of amplitude damping, phase damping, squeezed generalized amplitude damping noises, while entanglement-based protocols turn out to be preferable in the presence of collective noises. It is also observed that the effect of noise depends upon the number of rounds of quantum communication involved in a scheme of quantum communication. Further, it is observed that squeezing, a completely quantum mechanical resource present in the squeezed generalized amplitude channel, can be used in a beneficial way as it may yield higher fidelity compared to the corresponding zero squeezing case.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a comprehensive analysis of quasiprobability distributions for spin-qubit systems under general open system effects, including both pure dephasing as well as dissipation.

48 citations

Journal ArticleDOI
TL;DR: In this article, the dynamics of entanglement in a two-qubit system interacting with a squeezed thermal bath via a dissipative system-reservoir interaction with the system and reservoir assumed to be in a separable initial state was studied by making use of concurrence as well as a recently introduced measure of mixed state entenglement via a probability density function.

47 citations

Journal ArticleDOI
TL;DR: Single-qubit dissipative and non-dissipative channels, set in the general scenario of a system’s interaction with a squeezed thermal bath, are compared in the Choi isomorphism framework, to bring out their contrasting rank and geometric properties.
Abstract: Single-qubit dissipative and non-dissipative channels, set in the general scenario of a system's interaction with a squeezed thermal bath, are compared in the Choi isomorphism framework, to bring out their contrasting rank and geometric properties. The equivalence of commutativity between the signal states and the Kraus operators to that between the system and interaction Hamiltonian, and thus to non-dissipativeness, is pointed out. Two distinct unitarily equivalent Kraus representations of the dissipative channel, one based on the Choi isomorphism, and the other based on an ansatz, are used to illustrate that the orthogonality of Kraus operators under the Hilbert---Schmidt inner product is not a unitary invariant. Unlike the non-dissipative (Pauli) channels, the dissipative (squeezed generalized amplitude damping) channels do not form a convex set. Further, whereas the rank of Pauli channels can be any positive integer up to 4, that of the amplitude damping ones is either 2 or 4. In the latter case, a noise range is identified where environmental squeezing counteracts the effect of thermal decoherence.

45 citations

References
More filters
Journal ArticleDOI
TL;DR: In this article, the dynamics of the quantum phase distribution associated with the reduced density matrix of a system, as the system evolves under the influence of its environment with an energy-preserving quantum nondemolition (QND) type of coupling, are analyzed.
Abstract: We quantitatively analyze the dynamics of the quantum phase distribution associated with the reduced density matrix of a system, as the system evolves under the influence of its environment with an energy-preserving quantum nondemolition (QND) type of coupling. We take the system to be either an oscillator (harmonic or anharmonic) or a two-level atom (or equivalently, a spin-1/2 system), and model the environment as a bath of harmonic oscillators, initially in a general squeezed thermal state. The impact of the different environmental parameters is explicitly brought out as the system starts out in various initial states. The results are applicable to a variety of physical systems now studied experimentally with QND measurements.

29 citations

Journal ArticleDOI
TL;DR: In this paper, a model of environment-induced dissipationless decoherence of a quantum system where the system is coupled to the bath degrees of freedom via the system Hamiltonian itself was considered.
Abstract: We consider a model of environment-induced dissipationless decoherence of a quantum system where the system is coupled to the bath degrees of freedom via the system Hamiltonian itself. We solve exactly for the reduced density operator of the system for an arbitrary spectral density of the thermal bath and also write down an exact master equation in the Lindblad form. We compare and contrast the above results with those obtained by considering the system frequencies to be randomly modulated as in stochastic models. We observe that a coupling to the bath as above necessarily induces a Kerr-like coherent contribution in the reduced dynamics of the system. This Kerr-like term is a reflection of the quantum nature of the bath and cannot be obtained from stochastic models. For the special case of a harmonic oscillator we consider the influence of decoherence and its relation with phase diffusion. Our numerical results exhibit oscillations in the evolution of system variables which overall is a signature of the quantum nature of the environment.

23 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that decoherence can be useful for practical quantum computation, in particular for the effective erasure of quantum memory in order to initialize the state of the quantum computer.

18 citations

Journal ArticleDOI
TL;DR: In this article, the Lindblad approach to continuous quantum measurements is applied to a system composed of a two-level atom interacting with a stationary quantized electromagnetic field through a dispersive coupling fulfilling quantum nondemolition criteria.
Abstract: The Lindblad approach to continuous quantum measurements is applied to a system composed of a two-level atom interacting with a stationary quantized electromagnetic field through a dispersive coupling fulfilling quantum nondemolition criteria. Two schemes of measurements are examined. The first one consists in measuring the atomic electric dipole, which indirectly allows one to infer the photon distribution inside the cavity. The second one schematizes a measurement of photon momentum, which permits to describe the atomic level distribution. Decoherence of the corresponding reduced density matrices is studied in detail for both cases, and its relationship to recent experiments is finally discussed.

17 citations