共查询到20条相似文献,搜索用时 0 毫秒
1.
M.-M. He G. Chen J.-Q. Liang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):581-583
In this paper we investigate the Berry phase in Tavis-Cummings model in the
rotating wave approximation. The dipole-dipole interaction between the atoms
is considered. The eigenfunctions of the system are obtained and thus the
Berry phase is evaluated explicitly in terms of the introduction of the
phase shift. It is shown that the Berry phase can be easily controlled by
the atom-cavity coupling strength, the cavity frequency detuning, which can
be important in applications in geometric quantum computing. 相似文献
2.
J.-B. Liu J.-H. Li X.-Y. Lü A. Zheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):601-606
In this paper, we investigate the geometric phase of a composite system which is composed of two spin-
particles driven by a
time-varying magnetic field. Firstly, we consider the special case that only one subsystem driven by time-varying magnetic
field. Using the quantum jump
approach, we calculate the geometric phase associated with the adiabatic evolution of the system subjected to decoherence.
The results show that the lowest
order corrections to the phase in the no-jump trajectory is only quadratic in decoherence coefficient. Then, both subsystem
driven by time-varying magnetic
field is considered, we show that the geometric phase is related to the exchange-interaction coefficient and polar angle of
the magnetic field. 相似文献
3.
S. Banerjee R. Srikanth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):335-344
We study the geometric phase of an open two-level quantum
system under the influence of a squeezed, thermal environment for both
non-dissipative as well as dissipative system-environment
interactions. In the non-dissipative case, squeezing is found to have
a similar influence as temperature, of suppressing geometric phase,
while in the dissipative case, squeezing tends to counteract the
suppressive influence of temperature in certain regimes. Thus, an
interesting feature that emerges from our work is the contrast in the
interplay between squeezing and thermal effects in non-dissipative and
dissipative interactions. This can be useful for the practical
implementation of geometric quantum information processing. By
interpreting the open quantum effects as noisy channels, we make the
connection between geometric phase and quantum noise processes
familiar from quantum information theory. 相似文献
4.
Xin Li;Yu Shi 《Europhysics letters》2013,103(2)
We investigate the decoherence effect of a bosonic bath on the Berry phase of a spin- in a time-dependent magnetic field, without making the Markovian approximation. A two-cycle process resulting in a pure Berry phase is considered. The low-frequency quantum noise significantly affects the Berry phase. In the adiabatic limit, the high-frequency quantum noise only has a small effect. The result is also valid in some more general situations.https://doi.org/10.1209/0295-5075/103/20005 相似文献
5.
D. Geberth O. Kern G. Alber I. Jex 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):381-394
Two possible applications of random decoupling are discussed.
Whereas so far decoupling methods have been considered merely for quantum memories,
here it is demonstrated that random decoupling is also a convenient tool for stabilizing quantum algorithms. Furthermore,
a decoupling scheme is presented which involves a random decoupling method
compatible with detected-jump error correcting quantum codes. With this combined error correcting strategy it is possible
to stabilize quantum information against both spontaneous decay and static imperfections of a qubit-based quantum information
processor in an efficient way. 相似文献
6.
G. Benenti S. Felloni G. Strini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):389-396
We study the stability under quantum noise effects of the quantum privacy amplification protocol for the purification of entanglement
in quantum cryptography. We assume that the E91 protocol is used by two communicating parties (Alice and Bob) and that the
eavesdropper Eve uses the isotropic Bužek-Hillery quantum copying machine to extract information.
Entanglement purification is then operated by Alice and Bob by means of the quantum privacy amplification protocol and we
present a systematic numerical study of the impact of all possible
single-qubit noise channels on this protocol. We find that both the qualitative behavior of the fidelity of the purified state
as a function of the number of purification steps and
the maximum level of noise that can be tolerated by the protocol strongly depend on the specific noise channel. These results
provide valuable information for experimental implementations of the quantum privacy amplification protocol. 相似文献
7.
P. J. Salas 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):365-373
The decoherence effect on Grover algorithm has been studied numerically
through a noise modelled by a depolarizing channel. Two types of error are
introduced characterizing the qubit time evolution and gate application, so
the noise is directly related to the quantum network construction. The
numerical simulation concludes an exponential damping law for the successive
probability of the maxima as time increases. We have obtained an
allowed-error law for the algorithm: the error threshold for the allowed
noise behaves as εth(N) ∼1/N1.1 (N being the
size of the data set). As the power of N is almost one, we consider the
Grover algorithm as robust to a certain extent against decoherence. This law
also provides an absolute threshold: if the free evolution error is greater
than 0.043, Grover algorithm does not work for any number of qubits affected
by the present error model. The improvement in the probability of success,
in the case of two qubits has been illustrated by using a fault-tolerant
encoding of the initial state by means of the [[7,1,3]] quantum code. 相似文献
8.
X.-Z. Yuan K.-D. Zhu H.-S. Goan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):375-380
In the thermodynamic limit, we present an exact
calculation of the time dynamics of a central spin coupling with
its environment at finite temperatures. The interactions belong to
the Heisenberg XY type. The case of an environment with finite
number of spins is also discussed. To get the reduced density
matrix, we use a novel operator technique which is mathematically
simple and physically clear, and allows us to treat systems and
environments that could all be strongly coupled mutually and
internally. The expectation value of the central spin and the von
Neumann entropy are obtained. 相似文献
9.
Xin Li;Yu Shi 《Europhysics letters》2013,102(4)
We study quantum decoherence of single-qubit and two-qubit Aharonov-Anandan (AA) geometric phase gates realized in a multistep scheme. Each AA gate is also compared with the dynamical phase gate performing the same unitary transformation within the same time period and coupled with the same environment, which is modeled as harmonic oscillators. It is found that the fidelities and the entanglement protection of the AA phase gates are enhanced by the states being superpositions of different eigenstates of the environmental coupling, and the noncommutativity between the qubit interaction and the environmental coupling.https://doi.org/10.1209/0295-5075/102/40011 相似文献
10.
Chang Wang;Zhenping Guo 《Europhysics letters》2018,124(4)
Control errors and decoherence are two main obstacles for realization of quantum computation. Nonadiabatic holonomic quantum computation in decoherence-free subspaces can protect quantum gates from both control errors and decoherence, and, therefore, it has received increasing attention. The original protocol of nonadiabatic holonomic quantum computation in decoherence-free subspaces needs two loops in the Grassmann manifold to generate an arbitrary nonadiabatic holonomic one-qubit gate. In this paper, we proposed a protocol of nonadiabatic holonomic quantum computation in decoherence-free subspaces, where an arbitrary one-qubit gate is generated by only a single loop in the Grassmann manifold and an entangling two-qubit gate assisted by two single-qubit gates can be used to construct a two-qubit controlled unitary gate. In addition, the encoding of our protocol for nonadiabatic holonomic gates requires a lower number of physical qubits compared with previous schemes. Our scheme not only maintains the merits of the original protocol but it also avoids the extra work of combining two gates to realize an arbitrary one-qubit gate.https://doi.org/10.1209/0295-5075/124/40003 相似文献
11.
Vahid Azimi Mousolou 《Europhysics letters》2018,121(2)
A fundamental requirement of quantum information processing is the protection from the adverse effects of decoherence and noise. Decoherence-free subspaces and geometric processing are important steps of quantum information protection. Here, we provide a new experimentally feasible scheme to combine decoherence-free subspaces with nonadiabatic geometric manipulations to attain a universal quantum computation. The proposed scheme is different from previous proposals and is based on the typical XY interaction coupling, which can be set up in various nano-engineered systems and therefore open up for realization of nonadiabatic holonomic quantum computation in decoherence-free subspaces.https://doi.org/10.1209/0295-5075/121/20004 相似文献
12.
Spin interaction Hamiltonians are obtained from the unitary Yang-Baxter -matrix. Based on which, we study Berry phase and quantum criticality in the Yang-Baxter systems. 相似文献
13.
R. Srikanth S. Banerjee 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):217-227
We develop an information theoretic interpretation of the number-phase complementarity in atomic systems, where phase is treated
as a continuous positive operator valued measure (POVM). The relevant uncertainty principle is obtained as an upper bound
on a sum of knowledge of these two observables for the case of two-level systems. A tighter bound characterizing the uncertainty
relation is obtained numerically in terms of a weighted knowledge sum involving these variables. We point out that complementarity
in these systems departs from mutual unbiasededness in two significant ways: first, the maximum knowledge of a POVM variable
is less than log (dimension) bits; second, surprisingly, for higher dimensional systems, the unbiasedness may not be mutual
but unidirectional in that phase remains unbiased with respect to number states, but not vice versa. Finally, we study the
effect of non-dissipative and dissipative noise on these complementary variables for a single-qubit system. 相似文献
14.
D. Braun 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):103-108
The interaction of two–level atoms with a common heat bath leads to an effective interaction between the atoms, such that
with time the internal degrees of the atoms become correlated or even entangled. If part of the atoms remain unobserved this
creates
additional indirect decoherence for the selected atoms, on top of the direct decoherence due to the interaction with the heat
bath. I show that indirect decoherence can drastically increase and
even dominate the decoherence for sufficiently large times. I investigate indirect decoherence through thermal black body
radiation quantitatively for atoms trapped at regular positions in an optical lattice as well as for atoms at random positions
in a cold gas, and show how indirect
decoherence can be controlled or even suppressed through experimentally accessible parameters. 相似文献
15.
O. V. Zhirov D. L. Shepelyansky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(2):405-408
Using the methods of quantum trajectories
we study effects of dissipative decoherence on the accuracy
of the Grover quantum search algorithm.
The dependence on the number of qubits and
dissipation rate are determined and tested numerically
with up to 16 qubits. As a result,
our numerical and analytical studies give
the universal law for decay of fidelity and
probability of searched state which are induced by dissipative
decoherence effects. This law is in agreement with
the results obtained previously for quantum chaos algorithms. 相似文献
16.
Zhi Wang;Chang Xu 《Europhysics letters》2019,126(5)
We investigate the geometric phase for a two-level atom interacting with massless scalar field in the background spacetime of a cosmic string with torsion in the framework of open quantum systems. We show that the geometric phase depends on not only the inherent properties of this atom but also on the topological properties of the background spacetime. The correction to the geometric phase of the atom derives from a composite effect of the cosmic string and screw dislocation associated with the curvature and torsion,respectively. The numerical results of the correction to the geometric phase are also present. It is seen that the modification of the phase oscillates around zero and the amplitude of the correction decreases gradually,with the increase of the distance r between the atom and line defects. When the atom gets close to the line defects,the correction will increase significantly but finally tend to a finite value. The behavior of the geometric phase with the variation of the atomic position in three different types of topological defect spacetimes,i.e. ,the cosmic string spacetime,screw dislocation spacetime and cosmic string spacetime with torsion,are also shown. We note that the geometric phase in the case of cosmic string spacetime is different from that of other two spacetimes,which suggests that the presence of torsion can significantly affect the geometric phase of the atom,especially in the region near the topological defects. In addition,the geometric phase for the two-level atom which results from the thermal fluctuation of the thermal bath is studied. It is shown that the geometric phase increases with the growth of the temperature T .https://doi.org/10.1209/0295-5075/126/50005 相似文献
17.
X. L. Huang;X. X. Yi 《Europhysics letters》2008,82(5)
The geometric phases of a two-level atom interacting with non-Markovian environments are calculated and the non-Markovian effects on the geometric phases are discussed in this paper. Three kinds of methods that describe the non-Markovian process, projection superoperator technique, memory kernel master equation and post-Markovian master equation, are used in the discussions. The results show that when the dissipation rate is large, the non-Markovian effects change the geometric phase more strikingly than the small one. https://doi.org/10.1209/0295-5075/82/50001 相似文献
18.
Geometric phases are investigated for a Josephson qubit interacting with the Markovian and non-Markovian environments at arbitrary temperature according to a kinematic approach. In order to obtain the condition allowing experimental observation of geometric phase, we also estimate the decoherence times. The result shows that the Aharonov-Anandan phase may be different from the Berry phase under the environment perturbations. By comparing with the numerical result of the geometric phase as a function of the initial angle, we find that at low temperature, the effect of Markovian environment is larger than the non-Markovian one on the geometric phase. An approach is proposed to understand the accumulative effects of the geometric phase and its robustness to high-frequency noise, which may be helpful for geometric quantum information processing.https://doi.org/10.1209/0295-5075/96/40011 相似文献
19.
Qiong-Gui Lin Xin-Jian Hu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(3):235-241
We study the influence of a contact (or delta) potential
on the Aharonov-Bohm scattering of nonrelativistic particles. In
general the contact potential has no effect on the scattering as
expected. However, when the magnetic flux and the strength of the
contact potential take some special values, the Aharonov-Bohm
scattering cross-section is manifestly changed. It is shown that
these special values correspond to the simultaneous existence of two
half-bound states in two adjacent angular momentum channels. Two
limiting processes are presented to deal with the singularity of the
contact potential and results of the same nature are obtained. 相似文献
20.
J. Gemmer M. Michel 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):517-528
We consider discrete quantum systems coupled to finite environments which may possibly consist of only one particle in contrast
to the standard baths which usually consist of continua of oscillators, spins, etc.
We find that such finite environments may, nevertheless, act as thermostats, i.e., equilibrate the system though not necessarily
in the way predicted by standard open system techniques.
Thus, we apply a novel technique called the Hilbert space Average Method (HAM) and verify its results numerically. 相似文献