共查询到20条相似文献,搜索用时 31 毫秒
1.
Taking into account the main noises in superconducting charge qubits (SCQs), we propose a feasible scheme to realize quantum computing (QC) in a specially-designed decoherence-free subspace (DFS). In our scheme two physical qubits are connected with a common inductance to form a strong coupling subsystem, which acts as a logical qubit. Benefiting from the well-designed DFS, our scheme is helpful to suppress certain decoherence effects. 相似文献
2.
Z.-Y. Xue S. L. Zhu Z. D. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):223-228
We propose a scheme to implement quantum computation in
decoherence-free subspace with superconducting devices inside a
cavity by unconventional geometric manipulation. Universal
single-qubit gates in encoded qubit can be achieved with cavity
assisted interaction. A measurement-based two-qubit Controlled-Not
gate is produced with parity measurements assisted by an auxiliary
superconducting device and followed by prescribed single-qubit
gates. The measurement of currents on two parallel devices can
realize a projective measurement, which is equivalent to the parity
measurement on the involved devices. 相似文献
3.
An experimentally feasible strong coupling system between a spin ensemble and a superconducting qubit is studied. The coupling strength can be exponentially enhanced by applying the squeezing transformations to the system. By means of the two spin ensembles commonly coupled to a superconducting qubit, a set of universal nonadiabatic holonomic single‐qubit quantum gates can be realized in a decoherence‐free subspace. Furthermore, this proposal is robust with respect to decay of the system parameters, and it is experimentally feasible with currently available technology. 相似文献
4.
The effectiveness of decoherence suppression schemes is explored using quantum bits (qubits) stored in Li np Rydberg states. Following laser excitation, pulsed electric fields coherently control the electronic spin-orbit coupling, facilitating qubit creation, manipulation, and measurement. Spin-orbit coupling creates an approximate decoherence-free subspace for extending qubit storage times. However, sequences of fast NOT operations are found to be substantially more effective for preserving coherence. 相似文献
5.
Xiao-Qiang Shao Li Chen Shou Zhang Yong-Fang Zhao 《International Journal of Theoretical Physics》2009,48(10):2793-2799
A scheme for implementing a conditional z gate in the decoherence-free subspace of superconducting quantum-interference devices (SQUIDs) is presented based on the
dispersive interaction. Each logic qubit is encoded in the ground states of two rf SQUIDs, which own lower energy and can
be relatively stable in operation. By switching on/off the classical pulses and selecting the gating time appropriately, a
high fidelity is obtained. Moreover, this scheme can be generalized to the multi-qubit case without changing the gating time. 相似文献
6.
Bourennane M Eibl M Gaertner S Kurtsiefer C Cabello A Weinfurter H 《Physical review letters》2004,92(10):107901
Decoherence-free states protect quantum information from collective noise, the predominant cause of decoherence in current implementations of quantum communication and computation. Here we demonstrate that spontaneous parametric down conversion can be used to generate four-photon states which enable the encoding of one qubit in a decoherence-free subspace. The immunity against noise is verified by quantum state tomography of the encoded qubit. We show that particular states of the encoded qubit can be distinguished by local measurements on the four photons only. 相似文献
7.
One-step implementing three-qubit phase gate via manipulating rf SQUID qubits in the decoherence-free subspace with respect to cavity decay
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)
We present a scheme for implementing a three-qubit phase
gate via manipulating rf superconducting quantum interference device
(SQUID) qubits in the decoherence-free subspace with respect to
cavity decay. Through appropriate changes of the coupling constants
between rf SQUIDs and cavity, the scheme can be realized only in one
step. A high fidelity is obtained even in the presence of
decoherence. 相似文献
8.
This Letter presents a two-dimensional nuclear magnetic resonance (NMR) approach for constructing a two-logical-qubit decoherence-free subspace (DFS) by using four multiple-quantum coherences of a CH3 spin system as logical qubits. The three protons in this spin system are magnetically equivalent and can only be used as a single qubit in one-dimensional NMR. We have experimentally demonstrated that our DFS can protect against more types of decoherences than those of the one composed of four noisy physical qubits all with different chemical shifts. This idea may provide new insights into extending qubit systems in the sense that it effectively utilizes the magnetically equivalent nuclei. 相似文献
9.
Xiao Yao Wang ZiWu Shi Lin Jiang XiangWei Li ShuShen Wang LinWang 《中国科学:物理学 力学 天文学(英文版)》2020,63(7):1-11
Heat-bath algorithmic cooling(HBAC) has been proven to be a powerful and effective method for obtaining high polarization of the target system. Its cooling upper bound has been recently found using a specific algorithm, the partner pairing algorithm(PPAHBAC). It has been shown that by including cross-relaxation, it is possible to surpass the cooling bounds. Herein, by combining cross-relaxation and decoherence-free subspace, we present a two-qubit reset sequence and then generate a new algorithmic cooling(AC) technique using irreversible polarization compression to further surpass the bound. The proposed two-qubit reset sequence can prepare one of the two qubits to four times the polarization of a single-qubit reset operation in PPA-HBAC for low polarization. When the qubit number is large, the cooling limit of the proposed AC is approximately five times as high as the PPA-HBAC. The results reveal that cross-relaxation and decoherence-free subspace are promising resources to create new AC for higher polarization. 相似文献
10.
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
11.
ZENG Hao-Sheng NIE Jian-Jun KUANG Le-Man 《理论物理通讯》2006,46(3):447-452
We study the stability of decoherence-free subspaces under stochastic phase fluctuations by analytically and numerically evaluating the fidelity of the corresponding decoherence-free subspace bases with stochastic phase fluctuations under the evolution of environment. The environment is modeled by a bath of oscillators with infinite degrees of freedom and the register-bath coupling is chosen to be a general dissipation-decoherence form. It is found that the decoherence-free subspaces take on good stability in the case of small dissipation and small phase fluctuations. 相似文献
12.
We study the stability of decoherence-free subspaces under stochastic phase fluctuations by analytically and numerically evaluating the fidelity of the corresponding decoherence-free subspace bases with stochastic phase fluctuations under the evolution of environment. The environment is modeled by a bath of oscillators with infinite degrees of freedom and the register-bath coupling is chosen to be a general dissipation-decoherence form. It is found that the decoherence-free subspaces take on good stability in the case of small dissipation and small phase fluctuations. 相似文献
13.
In this paper, we study single-qubit and single-user quantum repeaters based on CNOT gates under decoherence using the Kraus-operator
representations of decoherence. We investigate the influence of decoherence on the information-disturbance trade-off of quantum
repeaters. It is found that decoherence may lead to the appearance of three subspaces, called as the normal subspace, the
anomalous subspace, and the decoherence-free subspace (DFS), respectively. It is indicated that in the normal subspace decoherence
decreases the transmission and estimation fidelities, in the anomalous subspace decoherence enhances these fidelities, and
in the DFS these fidelities do not change. The concept of the quality factor is introduced to evaluate the quality of the
quantum repeater. It is indicated that the quality factor can be efficiently controlled and manipulated by changing the initial
state of the probe qubit. It is found that under certain conditions the quantum repeater can be optimal even in the presence
of decoherence.
相似文献
14.
Langer C Ozeri R Jost JD Chiaverini J Demarco B Ben-Kish A Blakestad RB Britton J Hume DB Itano WM Leibfried D Reichle R Rosenband T Schaetz T Schmidt PO Wineland DJ 《Physical review letters》2005,95(6):060502
We demonstrate experimentally a robust quantum memory using a magnetic-field-independent hyperfine transition in 9Be+ atomic ion qubits at a magnetic field B approximately = 0.01194 T. We observe that the single physical qubit memory coherence time is greater than 10 s, an improvement of approximately 5 orders of magnitude from previous experiments with 9Be+. We also observe long coherence times of decoherence-free subspace logical qubits comprising two entangled physical qubits and discuss the merits of each type of qubit. 相似文献
15.
Wallraff A Schuster DI Blais A Frunzio L Majer J Devoret MH Girvin SM Schoelkopf RJ 《Physical review letters》2005,95(6):060501
In a Rabi oscillation experiment with a superconducting qubit we show that a visibility in the qubit excited state population of more than 95% can be attained. We perform a dispersive measurement of the qubit state by coupling the qubit non-resonantly to a transmission line resonator and probing the resonator transmission spectrum. The measurement process is well characterized and quantitatively understood. In a measurement of Ramsey fringes, the qubit coherence time is larger than 500 ns. 相似文献
16.
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
17.
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
18.
Tian L 《Physical review letters》2010,105(16):167001
Superconducting qubits connected in an array can form quantum many-body systems such as the quantum Ising model. By coupling the qubits to a superconducting resonator, the combined system forms a circuit QED system. Here, we study the nonlinear behavior in the many-body state of the qubit array using a semiclassical approach. We show that sudden switchings as well as a bistable regime between the ferromagnetic phase and the paramagnetic phase can be observed in the qubit array. A superconducting circuit to implement this system is presented with realistic parameters. 相似文献
19.
Marcos D Wubs M Taylor JM Aguado R Lukin MD Sørensen AS 《Physical review letters》2010,105(21):210501
We propose a method to achieve coherent coupling between nitrogen-vacancy (NV) centers in diamond and superconducting (SC) flux qubits. The resulting coupling can be used to create a coherent interaction between the spin states of distant NV centers mediated by the flux qubit. Furthermore, the magnetic coupling can be used to achieve a coherent transfer of quantum information between the flux qubit and an ensemble of NV centers. This enables a long-term memory for a SC quantum processor and possibly an interface between SC qubits and light. 相似文献
20.
Gustavsson S Bylander J Yan F Forn-Díaz P Bolkhovsky V Braje D Fitch G Harrabi K Lennon D Miloshi J Murphy P Slattery R Spector S Turek B Weir T Welander PB Yoshihara F Cory DG Nakamura Y Orlando TP Oliver WD 《Physical review letters》2012,108(17):170503
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence. 相似文献