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1.
We propose a novel quantum device in which a double carbon nanotube is embedded inside a suspended semiconductor slab. We theoretically investigate, in terms of a perturbation treatment based on a unitary transformation, the dynamics of the charge qubit in relation to the device. The phonon-induced decoherence and the quality of the qubit are analyzed in detail after a derivation of the phonon spectral density. It is shown that a charge qubit of high quality can be obtained due to the inhibition of the electron–phonon coupling in the confined structure of the slab, suggesting that the novel quantum device is a good candidate for quantum information processing. 相似文献
2.
We investigate theoretically the dynamics of a charge qubit (double quantum dot system) coupled electrostatically with the double-dot detector. The qubit charge oscillations and the detector current are calculated using the equation of motion method for appropriate correlation functions. In order to find the best detector performance (i.e. the detector current signal follows as well as possible the qubit charge oscillations) we consider different qubit-detector geometries. The optimal setup was found for the qubit lying parallel to the detector quantum dots for which we observed very good detector performance together with weak decoherence of the system. It is also shown that the asymptotic detector current (flowing in response to the limited in time qubit-detector interaction) fully reproduces the qubit dynamics. 相似文献
3.
Fay A Hoskinson E Lecocq F Lévy LP Hekking FW Guichard W Buisson O 《Physical review letters》2008,100(18):187003
We have realized a tunable coupling over a large frequency range between an asymmetric Cooper pair transistor (charge qubit) and a dc SQUID (phase qubit). Our circuit enables the independent manipulation of the quantum states of each qubit as well as their entanglement. The measurement of the charge qubit's quantum states is performed by an adiabatic quantum transfer from the charge to the phase qubit. The measured coupling strength is in agreement with an analytic theory including a capacitive and a tunable Josephson coupling between the two qubits. 相似文献
4.
Modified SQUID Operator Equation for a Single-Qubit Structure Coupled to a Quantum Resonator
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Role of self-inductance in superconducting quantum interference device (SQUID) charge qubit is considered. It is found that when an SQUID charge qubit is coupled to a quantum LC resonator, the SQUID voltage operator equation is modified in accompanying with the modification of operator Faraday equation describing the inductance. It is shown that when the extra energy is applied to the junction, the mean phase will be squeezed according to a damping factor. 相似文献
5.
We study quantum coherence in a semiconductor charge qubit formed from a GaAs double quantum dot containing a single electron. Voltage pulses are applied to depletion gates to drive qubit rotations and noninvasive state readout is achieved using a quantum point contact charge detector. We measure a maximum coherence time of ~7 ns at the charge degeneracy point, where the qubit level splitting is first-order insensitive to gate voltage fluctuations. We compare measurements of the coherence time as a function of detuning with numerical simulations and predictions from a 1/f noise model. 相似文献
6.
A hybrid quantum computing scheme is studied where the
hybrid qubit is made of an ion trap qubit serving as the
information storage and a solid-state charge qubit serving as the
quantum processor, connected by a superconducting cavity. In this
paper, we extend our previous work [CITE] and study the
decoherence, coupling and scalability of the hybrid system. We
present our calculations of the decoherence of the coupled ion-charge system due to the charge fluctuations in the solid-state
system and the dissipation of the superconducting cavity under
laser radiation. A gate scheme that exploits rapid state flips of
the charge qubit to reduce decoherence by the charge noise is
designed. We also study a superconducting switch that is inserted
between the cavity and the charge qubit and provides tunable
coupling between the qubits. The scalability of the hybrid scheme
is discussed together with several potential experimental
obstacles in realizing this scheme. 相似文献
7.
We introduce a new type of superconducting charge qubit that has a V-shaped energy spectrum and uses quantum interference to provide independently tunable qubit energy and coherent coupling to a superconducting cavity. Dynamic access to the strong coupling regime is demonstrated by tuning the coupling strength from less than 200 kHz to greater than 40 MHz. This tunable coupling can be used to protect the qubit from cavity-induced relaxation and avoid unwanted qubit-qubit interactions in a multiqubit system. 相似文献
8.
We study the influence of screening effect on quantum decoherence for charge qubit and the process of quantum information storage. When the flux produced by the circulating current in SQUID loop is considered, screening effect is formally characterized by a LC resonator. Using large-detuning condition and Fröhlich transformation in the qubit-cavity-resonator system, we calculate the decoherence factor for charge qubit and the effective qubit-cavity Hamiltonian. The decoherence factor owns a factorized structure, it shows that screening effect is a resource of decoherence for charge qubit. The effective Hamiltonian shows that the screening effect results in a frequency shift for charge qubit and a modified qubit-cavity coupling constant induced by a LC resonator. 相似文献
9.
We investigate coherent time evolution of charge states (pseudospin qubit) in a semiconductor double quantum dot. This fully tunable qubit is manipulated with a high-speed voltage pulse that controls the energy and decoherence of the system. Coherent oscillations of the qubit are observed for several combinations of many-body ground and excited states of the quantum dots. Possible decoherence mechanisms in the present device are also discussed. 相似文献
10.
Schuster DI Wallraff A Blais A Frunzio L Huang RS Majer J Girvin SM Schoelkopf RJ 《Physical review letters》2005,94(12):123602
We have performed spectroscopy of a superconducting charge qubit coupled nonresonantly to a single mode of an on-chip resonator. The strong coupling induces a large ac Stark shift in the energy levels of both the qubit and the resonator. The dispersive shift of the resonator frequency is used to nondestructively determine the qubit state. Photon shot noise in the measurement field induces qubit level fluctuations leading to dephasing which is characteristic for the measurement backaction. A crossover in line shape with measurement power is observed and theoretically explained. For weak measurement a long intrinsic dephasing time of T2>200 ns of the qubit is found. 相似文献
11.
Hunkar Kayhan 《理论物理通讯》2011,56(1):139-143
We study the dynamics of the entropy correlations and entanglement in a system of interaction of a superconducting charge qubit with a single-mode resonant cavity subject to noise considered as two-state random phase telegraph noise. We show that although the noise has an apparent suppressing effect on the evolution of the entropies of the qubit and the field and also on the entanglement in the system, the entropy exchange between the qubit and the
field is independent of it during the time evolution of the system. 相似文献
12.
研究了初态为混合态的电荷量子比特与量子化光场之间的纠缠.通过求解系统的concurrence下限, 研究初态的混合度λ和失谐量Δ对系统纠缠随时间演化的影响. 在弱场中, 电荷量子比特初始是激发态的系统, 其纠缠度远远大于电荷量子比特初始是基态的系统, 并且Δ对系统的纠缠有明显的抑制作用. 在强场中, 电荷量子比特初始分别为激发态和基态时系统的纠缠演化接近一致, 初态混合度最高时系统的纠缠度最小, 并且Δ对系统纠缠的影响变弱.
关键词:
约瑟夫森结
纠缠
混合态
concurrence下限 相似文献
13.
We propose a scheme to implement quantum state transfer in a hybrid circuit quantum electrodynarnics (QED) system which consists of a superconducting charge qubit, a flux qubit, and a transmission line resonator (TLR). It is shown that quantum state transfer between the charge qubit and the flux qubit can be realized by using the TLR as the data bus. 相似文献
14.
We propose a single shot quantum measurement to determine the state of a Josephson charge quantum bit (qubit). The qubit is a Cooper pair box and the measuring device is a two junction superconducting quantum interference device (dc SQUID). This coupled system exhibits a close analogy with a Rydberg atom in a high Q cavity, except that in the present device we benefit from the additional feature of escape from the supercurrent state by macroscopic quantum tunneling, which provides the final readout. We test the feasibility of our idea against realistic experimental circuit parameters and by analyzing the phase fluctuations of the qubit. 相似文献
15.
The time evolution of a charge qubit coupled electrostatically with different detectors in the forms of single, double and triple quantum dot linear systems in the T-shaped configuration between two reservoirs is theoretically considered. The correspondence between the qubit quantum dot oscillations and the detector current is studied for different values of the inter-dot tunneling amplitudes and the qubit–detector interaction strength. We have found that even for a qubit coupled with a single QD detector, the coherent beat patterns appear in the oscillations of the qubit charge. This effect is more evident for a qubit coupled with double or triple-QD detectors. The beats can be also observed in both the detector current and the detector quantum dot occupations. Moreover, in the presence of beats the qubit oscillations hold longer in time in comparison with the beats-free systems with monotonously decaying oscillations. The dependence of the qubit dynamics on different initial occupations of the detector sites (memory effect) is also analyzed. 相似文献
16.
17.
We study the entanglement of the
superconducting charge qubit with the
quantized electromagnetic field in a microwave cavity. It can be controlled
dynamically by a classical external field threading the SQUID within the
charge qubit. Utilizing the controllable quantum entanglement, we can demonstrate the dynamic process of the quantum storage of information
carried by charge qubit. On the other hand, based on this engineered quantum
entanglement, we can also demonstrate a progressive decoherence of charge
qubit with quantum jump due to the coupling with the cavity field in
quasi-classical state. 相似文献
18.
We theoretically introduce a mesoscopic pendulum from a triple dot. The pendulum is fastened through a singly occupied dot (spin qubit). Two other strongly capacitively coupled islands form a double-dot charge qubit with one electron in excess oscillating between the two low-energy charge states (1,0) and (0,1). The triple dot is placed between two superconducting leads. Under realistic conditions, the main proximity effect stems from the injection of resonating singlet (valence) bonds on the triple dot. This gives rise to a Josephson current that is charge- and spin-dependent and, as a consequence, exhibits a distinct resonance as a function of the superconducting phase difference. 相似文献
19.
20.
M. Sebawe Abdalla A.-S. F. Obada A.-B. A. Mohamed E. M. Khalil 《International Journal of Theoretical Physics》2014,53(4):1325-1336
A single-mode microwave cavity field, coupled to its reservoir, interacting generally with a superconducting charge qubit is considered. Using a certain canonical transformation for the qubit states, the system is transformed into the usual Jaynes-Cummings model. The solution of the master equation of this system, in the case of a high-Q cavity is obtained. The temporal evolution of the population inversion is explored. The effects of cavity damping on the purity of the qubit, the field and the global system state are studied. It is found that due to the coupling between the system and environment, the purity is lost. The entanglement is compared with total correlation. It is found that, with the damping parameter, the asymptotic value of the correlation measure is not null, since the global system evolves to a classically correlated state. The negativity is used as an indicator of the degree of entanglement between the qubit and the field. The results indicate the sensitivity of these aspects to change of the damping parameter. 相似文献