共查询到20条相似文献,搜索用时 15 毫秒
1.
A simple Scheme for Generating an n-Qubit W State in a Trapped-Ion System without a Lamb-Dicke Limit
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A simple and scalable scheme is proposed to generate a n-qubit W state in a trapped-ion system without the Lamb-Dicke limit. The n-qubit W state can be generated by the interaction between the ions and the laser field if the collective mode is initially prepared in the single-phonon state and each ion is in the ground state. The scheme only requires a single laser and avoids laser manipulation of the individual ion. The time required to complete the process decreases with the number of ions. The present scheme is not limited to small values of the LD parameter, which greatly enhances operation speeds. 相似文献
2.
Influence of Multi-Photon Process on Entanglement of Interacting System of the Qubit and Thermal Field 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We study the system of a single qubit couples to a single mode thermal field according to a multi-photon Jaynes-Cummings-type interaction with phase decoherence. Both the time evolving entanglement and the stationary state entanglement are calculated by adopting the log-negativity as a measure. It is found that the multi-photonprocess can enhance the stationary state entanglement of this system and can enlarge the range of the parameter Δ/g and the mean photon number of initial thermal field in which the stationary state is distillable. 相似文献
3.
We propose a scheme to implement two-qubit controlled quantum phase
gate(CQPG) via a single trapped two-level ion located
in the standing wave field of a quantum cavity, in which the trap works
beyond the Lamb--Dicke limit.
When the
light field is resonant with the atomic transition
$|g\rangle\leftrightarrow|e\rangle$ of the ion located at the
antinode of the standing wave, we can perform CQPG between the
internal and external states of the trapped ion; while the frequency
of the light field is chosen to be resonant with the first red
sideband of the collective vibrational mode of the ion located at
the node of the standing wave, we can perform CQPG between the
cavity mode and the collective vibrational mode of the trapped ion.
Neither the Lamb--Dicke approximation nor the assistant classical
laser is needed. Also we can generate a GHZ state if assisted with
a classical laser. 相似文献
4.
The dependence of fidelity on the squeezing parameter in teleportation of the squeezed coherent states
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper investigates an analytical expression of teleportation fidelity in the teleportation scheme of a single mode of electromagnetic field.The fidelity between the original squeezed coherent state and the teleported one is expressed in terms of the squeezing parameter r and the quantum channel parameter(two-mode squeezed state) p.The results of analysis show that the fidelity increases with the increase of the quantum channel parameter p,while the fidelity decreases with the increase of the squeezing parameter r of the squeezed state.Thus the coherent state(r = 0) is the best quantum signal for continuous variable quantum teleportation once the quantum channel is built. 相似文献
5.
An Intuitive Expression for Inseparability Condition of a Two-Mode Squeezed Vacuum State in a Thermal Environment 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
LIFu-Li LIHong-Rong 《中国物理快报》2004,21(6):991-994
Considering the propagation of a two-mode optical field that is initially in a squeezed vacuum state in a thermalenvironment, we obtain an intuitive expression for inseparability condition of the two-mode mixed state which isgiven in the coherent state representation. This condition shows that the two modes have quantum entanglementif and only if the coefficient of the correlation term between the two modes is larger than that of the off-diagonalterm of each mode in the density matrix. We find that even if the quantum channel is dynamically coupled to thethermal environment, the fidelity for teleporting coherent states larger than 1/2 is still the criterion for quantum teleportation. We also show that the entanglement, squeezing and quantum teleportation conditions are alwaysconsistent with each other. 相似文献
6.
Faithfully probabilistic teleportation of an unknown atomic state and cavity field state with a single measurement
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper shows that, based on the single-photon JC model depicting the resonant interaction of a two-level atom with a single cavity mode, an unknown atomic state and cavity photon superposition state can be faithfully telcported with only a single measurement. The scheme is probabilistie, its success lies on the event that the sender atom (or the medi-atom, for teleportation of cavity field state) is detected in the higher state. The scheme is in contrast to the previous ones of using a maximally two-particle entangled state as quantum channel.[第一段] 相似文献
7.
This paper proposes a simple scheme to generate a
four-atom entangled cluster state in cavity quantum electrodynamics.
With the assistantce of a strong classical field the cavity is only
virtually excited and no quantum information will be transferred
from the atoms to the cavity during the preparation for a four-atom
entangled cluster state, and thus the scheme is insensitive to the
cavity field states and cavity decay. Assuming that deviation of
laser intensity is 0.01 and that of simultaneity for the interaction
is 0.01, it shows that the fidelity of the resulting four-atom
entangled cluster state is about 0.9886. The scheme can also be
used to generate a four-ion entangled cluster state in a hot
trapped-ion system. Assuming that deviation of laser intensity is
0.01, it shows that the fidelity of the resulting four-ion entangled
cluster state is about 0.9990. Experimental feasibility for
achieving this scheme is also discussed. 相似文献
8.
Production of Squeezed State of Single Mode Cavity Field by the Coupling of Squeezed Vacuum Field Reservoir in Nonautonomous Case 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The dissipative and decoherence properties as well as the asymptotic behaviour of the single mode electromagnetic field interacting with the time-dependent squeezed vacuum field reservoir are investigated in detail by using the algebraic dynamical method. With the help of the left and right representations of the relevant hw(4) algebra, the dynamical symmetry of the nonautonomous master equation of the system is found to be su(1, 1). The unique equilibrium steady solution is found to be the squeezed state and any initial state of the system is proven to approach the unique squeezed state asymptotically. Thus the squeezed vacuum field reservoir is found to play the role of a squeezing mold of the cavity field. 相似文献
9.
Teleportation of a two-atom entangled state using a single EPR pair in cavity QED 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We propose a scheme for teleporting a two-atom entangled state in
cavity quantum electrodynamics (QED). In the scheme, we choose a
single Einstein--Podolsky--Rosen (EPR) pair as the quantum channel which
is shared by the sender and the receiver. By using the atom--cavity-field
interaction and introducing an additional atom, we can teleport
the two-atom entangled state successfully with a probability of 1.0.
Moreover, we show that the scheme is insensitive to cavity decay
and thermal field. 相似文献
10.
We describe a protocol for telecloning a quantum state to M distant users via an ( M + 1)-particle W state, In the scheme, two atoms interact simultaneously with a highly detuned cavity mode with the assistance of a classical field. The scheme is insensitive to the cavity decay and the thermal field. Moreover, the Bell-state measurement can be achieved by detecting two atoms separately. Thus telecloning can be realized in a simple way. 相似文献
11.
Optical switch fabric plays an important role in building multiple-user optical quantum communication networks.Owing to its self-routing property and low complexity, a banyan network is widely used for building switch fabric. While,there is no efficient way to remove internal blocking in a banyan network in a classical way, quantum state fusion, by which the two-dimensional internal quantum states of two photons could be combined into a four-dimensional internal state of a single photon, makes it possible to solve this problem. In this paper, we convert the output mode of quantum state fusion from spatial-polarization mode into time-polarization mode. By combining modified quantum state fusion and quantum state fission with quantum Fredkin gate, we propose a practical scheme to build an optical quantum switch unit which is block free. The scheme can be extended to building more complex units, four of which are shown in this paper. 相似文献
12.
Entropy squeezing of the field interacting with a nearly degenerate V-type three-level atom
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The position- and momentum-entopic squeezing properties of the optical field in the system of a nearly degenerate three-level atom interacting with a single-mode field are investigated. Calculation results indicate that when the field is initially in the vacuum state, it may lead to squeezing of the position entropy or the momentum entropy of the field if the atom is prepared properly. The effects of initial atomic state and the splitting of the excited levels of the atom on field entropies are discussed in this case. When the initial field is in a coherent state, we find that position-entropy squeezing of the field is present even if the atom is prepared in the ground state. By comparing the variance squeezing and entropy squeezing of the field we confirm that entropy is more sensitive than variance in measuring quantum fluctuations. 相似文献
13.
ZHANG Xue ZHENG Tai-Yu ZHENG Li 《理论物理通讯》2008,50(10):955-960
The system of the Hamiltonian involving a driving part, a single mode part, and a two-mode squeezed one and a two-mode coupled one is discussed using the Lewis-Riesenfeld invariant theory. The time evolution operator is obtained. When the initial state is a coherent state, the quantum fluctuation of the system is calculated, and it is dependent on the squeezed part and the two-mode coupled part, but not dependent on the driving one. 相似文献
14.
SONG Ke-Hui ZHOU Zheng-Wei GUO Guang-Can 《理论物理通讯》2006,46(4):631-634
We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device (SQUID) qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed in two lower flux states, and the excited state [2〉 would not participate in the procedure. The SQUIDs undergo no transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum iogic in SQUID-system. 相似文献
15.
XIEWen-Fang ZHUWu 《理论物理通讯》2003,40(1):113-116
The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots are studied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method of numerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the binding energy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupled quantum dot as a function of the dot radius for different vaJues of the distance and the magnetic field strength. 相似文献
16.
Two narrow bandwidth photons interfering in an electromagnetically induced transparency (EIT) system
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this paper, we have analysed in detail the quantum interference of the degenerate narrowband two-photon state by using a Mach-Zehnder interferometer, in which an electromagnetically induced transparency (EIT) medium is placed in one of two interfering beams. Our results clearly show that it is possible to coherently keep the quantum state at a single photon level in the EIT process, especially when the transparent window of the EIT medium is much larger than the bandwidth of the single photon. This shows that the EIT medium is possibly a kind of memory or repeater for the narrowband photons in the areas of quantum communication and quantum computer. This kind of experiment is feasible within the current technology. 相似文献
17.
Chen Ding Xiao-Yue Xu Yun-Fei Niu Shuo Zhang Wan-Su Bao He-Liang Huang 《中国科学:物理学 力学 天文学(英文版)》2023,(3):62-69
Qubit measurement is generally the most error-prone operation that degrades the performance of near-term quantum devices,and the exponential decay of readout fidelity severely impedes the development of large-scale quantum information processing.Given these disadvantages, we present a quantum state readout method, named compression readout, that naturally avoids large multi-qubit measurement errors by compressing the quantum state into a single qubit for measurement. Our method generally outperf... 相似文献
18.
Resonant interaction scheme for GHZ state preparation and quantum phase gate with superconducting qubits in a cavity
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A scheme is proposed to generate GHZ state and realize quantum phase gate for superconducting qubits placed in a microwave cavity. This scheme uses resonant interaction between the qubits and the cavity mode, so that the interaction time is short, which is important in view of decoherence. In particular, the phase gate can be realized simply with a single interaction between the qubits and the cavity mode. With cavity decay being considered, the fidelity and success probability are both very close to unity. 相似文献
19.
This paper calculates the time evolution of the quantum mechanical
state of an electron by using variational method of Pekar type on
the condition of electric--LO-phonon strong coupling in a parabolic
quantum dot. It obtains the eigenenergies of the ground state and
the first-excited state, the eigenfunctions of the ground state and
the first-excited state This system in a quantum dot may be employed
as a two-level quantum system qubit. The superposition state
electron density oscillates in the quantum dot with a period when
the electron is in the superposition state of the ground and the
first-excited state. It studies the influence of the electric field
on the eigenenergies of the ground state, the first-excited state
and the period of oscillation at the different electron--LO-phonon
coupling constant and the different confinement length. 相似文献
20.
The decoy-state method is a useful method in resisting the attacks on quantum key distribution. However, how to choose the intensities of decoy states and the ratio of the decoy states and the signal state is still an open question. We present a simple formula to analyse the problem. We also give a simple method to derive the bounds of the necessary counting rates and quantum bit error rates for BB84 and SARG04; the latter was previously proposed by Scarani et al. [Phys. Rev. Lett. 92 (2004)057901] We then propose a multi-signal-state method which employs different coherent states either as the decoy state or as the signal state to carry out quantum key distribution. We find our protocol more efficient and feasible. 相似文献