共查询到20条相似文献，搜索用时 15 毫秒
1.
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
2.
We propose a technique that allows to simultaneously perform universal control of the evolution operator of a system and compensate for the first-order contribution of any Hermitian constant noise and the action of the environment. We show that, at least, a three-valued Hamiltonian is needed in order to protect the system against any such noise and propose an explicit algorithm for finding an appropriate control sequence. This algorithm is applied to numerically design a safe gate in an atomic qutrit.https://doi.org/10.1209/0295-5075/89/10011 相似文献
3.
Photons with orbital angular momentum provide an infinite-dimensional Hilbert space. Here,we study the propagation of such photons in atmospheric turbulence and obtain the Kraus operator representation for the decoherence-induced noise. We apply quantum error correction to suppress this decoherence. Specifically,we treat correction as an optimization problem in which the distance between the actual channel and the desired channel is minimized. This method provides significant channel fidelity enhancement irrespective of the turbulence strength.https://doi.org/10.1209/0295-5075/132/50005 相似文献
4.
Since masking of quantum information was introduced by Modi et al . in Modi K. et al .,Phys. Rev. Lett. ,120 (2018) 230501,many discussions on this topic have been published. In this paper,we explore the relationship between quantum multipartite maskers (QMMs) and quantum error-correcting codes (QECCs). We say that a subset Q of pure states of a system can be masked by an operator S into a multipartite system if all of the image states $S|psirangle $ $|psirangle $ Q have the same marginal states on each subsystem. We call such an S a QMM of Q . By establishing a necessary and sufficient condition for a set Q to be masked by an operator,we prove that a linear operator is a QMM of all pure states of a system if and only if its range is a QECC of any one-erasure channel. As an application,we prove that there is no universal maskers from into and then the states of cannot be masked into . This gives a consummation to a main result and leads to a negative answer to an open question in Li M.‐S. and Wang Y.‐L. ,Phys. Rev. A ,98 (2018) 062306. Another application is that arbitrary quantum states of can be completely hidden in correlations between any two subsystems of the tripartite system ,while arbitrary quantum states cannot be completely hidden in the correlations between subsystems of a bipartite system (Braunstein S. L. and Pati A. K. ,Phys. Rev. Lett. ,98 (2007) 080502).https://doi.org/10.1209/0295-5075/131/30005 相似文献
5.
We propose an alignment-free two-party polarization-entanglement transmission scheme for entangled photons by using only linear-optical elements,requiring neither ancillary photons nor calibrated reference frames. The scheme is robust against both the random channel noise and the instability of reference frames. Furthermore,the success probabilities for entanglement transmission are,in principle,improved to unity when active polarization controllers are used. The distinct characters of a simple structure,being easy to implement,and the high fidelity and efficiency make our protocol very useful for long-distance quantum communications and distributed quantum networks in practical applications. As an example,we give its application in a reference-frame-alignment-free quantum key distribution protocol with entanglement.https://doi.org/10.1209/0295-5075/127/60001 相似文献
6.
《Europhysics letters》2011,96(1)
The performance of sequences of designed pulses of finite length τ is analyzed for a bath of spins and it is compared with that of sequences of ideal, instantaneous pulses. The degree of the design of the pulse strongly affects the performance of the sequences. Non-equidistant, adapted sequences of pulses, which equal instantaneous ones up to , outperform equidistant or concatenated sequences. Moreover, they do so at low energy cost which grows only logarithmically with the number of pulses, in contrast to standard pulses with linear growth.https://doi.org/10.1209/0295-5075/96/10003 相似文献
7.
Tremendous research efforts have been invested in exploring and designing so-called shortcuts to adiabaticity. These are finite-time processes that produce the same final states that would result from infinitely slow driving. Most of these techniques rely on auxiliary fields and quantum control,which makes them rather costly to implement. In this Perspective we outline an alternative paradigm for optimal control that has proven powerful in a wide variety of situations ranging from heat engines over chemical reactions to quantum dynamics —thermodynamic control. Focusing on only a few,selected milestones we seek to provide a pedagogical entry point into this powerful and versatile framework.https://doi.org/10.1209/0295-5075/131/20001 相似文献
8.
We devise a new quantum key distribution scheme that is more efficient than the BB84 protocol. By pre-announcing the basis, Alice and Bob are more likely to use the same basis to prepare and measure the qubits, thus achieving a higher efficiency. The error analysis is revised and its security against any eavesdropping is proven briefly. Furthermore we show that, compared with the LCA scheme, our modification can be applied in more quantum channels.https://doi.org/10.1209/0295-5075/105/60003 相似文献
9.
The determinisitc entanglement concentration (DEC) protocol under local operations and classical communication (LOCC) for three-copy partially entangled states in bipartite systems is presented. The explicit elements of the operators used are calculated due to the general construction of the generalized measurement operator and the corresponding permutation matrices. The measurement is implemented based on the direct sum extension under the motivation to extend the initial state space with minimum number of ancillary dimensions. Morever, the concentration protocol is generalized to the DEC for n -copy multi-partite GHZ-class states. It is also pointed out that the formation of the measurement operator and the algorithms used to calculate its elements can be utilized in more general cases achieving the feasible entanglement transformation that is clarified by Nielsen's theorem, such as the transformation between arbitrary bipartite states in multicopy and high-dimensional cases and so does multi-partite GHZ-class states.https://doi.org/10.1209/0295-5075/104/10005 相似文献
10.
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
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.
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
13.
G.-D. Lin;S.-L. Zhu;R. Islam;K. Kim;M.-S. Chang;S. Korenblit;C. Monroe;L.-M. Duan 《Europhysics letters》2009,86(6)
We propose a large-scale quantum computer architecture by more easily stabilizing a single large linear ion chain in a very simple trap geometry. By confining ions in an anharmonic linear trap with nearly uniform spacing between ions, we show that high-fidelity quantum gates can be realized in large linear ion crystals under the Doppler temperature based on coupling to a near-continuum of transverse motional modes with simple shaped laser pulses.https://doi.org/10.1209/0295-5075/86/60004 相似文献
14.
We present a hybrid entanglement purification and concentration protocol for nuclear spin entangled states of nitrogen-vacancy (N-V) centers resorting to the ancillary photons and electrons. In the entanglement purification protocol,the mixed entangled states of the N-V centers can be purified with high fidelity using two pairs of entangled photons to interact with each electron in N-V centers. By performing local measurement on the electrons,the original entangled state can be obtained between the two remote parities. In the entanglement concentration protocol,the partially entangled states of the nuclear spin in N-V centers can be concentrated to the maximally entangled state by using an ancillary photon on one local user. The fidelity of the entangled state with different excited state decay rate and the relation between the yield and different decay rate are numerically simulated.https://doi.org/10.1209/0295-5075/126/40006 相似文献
15.
G. De Chiara A. Łoziński G. M. Palma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):179-183
The evolution of a two level system with a slowly varying Hamiltonian, modeled as a spin 1/2 in a slowly varying magnetic
field, and interacting with a quantum environment, modeled as a bath of harmonic oscillators is analyzed using a quantum Langevin
approach. This allows to easily obtain the dissipation time and the correction to the Berry phase in the case of an adiabatic
cyclic evolution. 相似文献
16.
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
17.
We explore the physics of the anisotropic compass model under the influence of perturbing Heisenberg interactions and present the phase diagram with multiple quantum phase transitions. The macroscopic ground-state degeneracy of the compass model is lifted in the thermodynamic limit already by infinitesimal Heisenberg coupling, which selects different ground states with symmetry depending on the sign and size of the coupling constants —then low-energy excitations are spin waves, while the compass states reflecting columnar order are separated from them by a macroscopic gap. Nevertheless, nanoscale structures relevant for quantum computation purposes may be tuned such that the compass states are the lowest-energy excitations, thereby avoiding decoherence, if a size criterion derived by us is fulfilled.https://doi.org/10.1209/0295-5075/91/40005 相似文献
18.
Wang Yao;Yu Luo 《Europhysics letters》2010,92(1)
In a coupled double-quantum-dot system, we present a theory for the interplay between electron and nuclear spins when the two-electron singlet state is brought into resonance with one triplet state in moderate external magnetic field. We show that the quantum interference between first-order and second-order hyperfine processes can lead to a feedback mechanism for manipulating the nuclear hyperfine fields. In a uniform external field, positive- and negative-feedback controls can be realized for the gradient of the longitudinal hyperfine field as well as the average transverse hyperfine field in the double dot. The negative feedback which suppresses fluctuations in the longitudinal nuclear field gradient can enhance the decoherence time of a singlet-triplet qubit to microsecond regime. We discuss the possibility of enhancing the decoherence time of each individual spin in a cluster of dots using the negative-feedback control on the transverse nuclear field.https://doi.org/10.1209/0295-5075/92/17008 相似文献
19.
X. Caillet C. Simon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):341-348
We analyze the achievable precision for single-qubit gates that
are based on off-resonant Raman transitions between two
near-degenerate ground states via a virtually excited state. In
particular, we study the errors due to non-perfect adiabaticity
and due to spontaneous emission from the excited state. For the
case of non-adiabaticity, we calculate the error as a function of
the dimensionless parameter χ=Δτ, where Δ is
the detuning of the Raman beams and τ is the gate time. For
the case of spontaneous emission, we give an analytical argument
that the gate errors are approximately equal to Λ
γ/Δ, where Λ is the rotation angle of the
one-qubit gate and γ is the spontaneous decay rate, and we
show numerically that this estimate holds to good approximation. 相似文献
20.
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