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1.
A goal of quantum information technology is to control the quantum state of a system, including its preparation, manipulation, and measurement. However, scalability to many qubits and controlled con-nectivity between any selected qubits are two of the major stumbling blocks to achieve quantum com-puting (QC). Here we propose an experimental method, using Josephson charge qubits, to efficiently solve these two central problems. The proposed QC architecture is scalable since any two charge qubits can be effectively coupled by an experimentally accessible inductance. More importantly, we formulate an efficient and realizable QC scheme that requires only one (instead of two or more) two-bit operation to implement conditional gates.  相似文献   

2.
We propose a new concept for a two-qubit gate operating on a pair of trapped ions based on laser coherent control techniques. The gate is insensitive to the temperature of the ions, works also outside the Lamb-Dicke regime, requires no individual addressing by lasers, and can be orders of magnitude faster than the trap period, which is presently the speed limit of all two-qubit proposals.  相似文献   

3.
The ion trap quantum information processor   总被引:8,自引:0,他引:8  
Received: 16 October 1996/Revised version: 2 April 1997  相似文献   

4.
Scaling ion trap quantum computation through fast quantum gates   总被引:1,自引:0,他引:1  
We propose a method to achieve scalable quantum computation based on fast quantum gates on an array of trapped ions, without the requirement of ion shuttling. Conditional quantum gates are obtained for any neighboring ions through spin-dependent acceleration of the ions from periodic photon kicks. The gates are shown to be robust to influence all the other ions in the array and insensitive to the ions' temperature.  相似文献   

5.
We theoretically propose a feasible scheme to perform quantum computing in decoherence-free subspaces (DFSs) with Cooper-pair box (CPB) qubits arrayed in a circuit QED architecture. Based on the cavity-bus assisted interaction, the selective and controllable interqubit couplings occur only by adjusting the individual gate pulses, by which we obtain the scalable DFS-encoded universal quantum gates to resist certain collective noises. Further analysis shows the protocol may implement the scalable fault-tolerant quantum computing with current experimental means.  相似文献   

6.
Zhi-Bo Feng 《Physics letters. A》2008,372(21):3773-3777
This Letter proposes a theoretical scheme for scalable quantum computing with charge-phase qubits inside a common cavity. Individually addressing the applied gate pulses, we obtain the switchable interqubit couplings mediated by the cavity mode, from which a universal set of logic gates can be constructed. In our scheme the interqubit couplings are completely feasible to perform conditional gates, and the classical microwaves cause negligible leakage errors.  相似文献   

7.
A crucial building block for quantum information processing with trapped ions is a controlled-NOT quantum gate. In this Letter, two different sequences of laser pulses implementing such a gate operation are analyzed using quantum process tomography. Fidelities of up to 92.6(6)% are achieved for single-gate operations and up to 83.4(8)% for two concatenated gate operations. By process tomography we assess the performance of the gates for different experimental realizations and demonstrate the advantage of amplitude-shaped laser pulses over simple square pulses. We also investigate whether the performance of concatenated gates can be inferred from the analysis of the single gates.  相似文献   

8.
We theoretically present a scheme to realize the scalable geometric quantum computing with Cooper-pair box (CPB) qubits in circuit QED. A one-dimensional transmission line resonator in circuit QED acting as quantum data bus generates a common cavity mode and interacts with each CPB. It is found that the interqubit couplings between any pair of qubits are switchable by individually adjusting the gate pulses applied to the selected CPBs. In this proposed scheme, we can both controllably and selectively address logic gates in geometric scenarios, which opens the possibility to implement the scalable fault-tolerant quantum computing with Josephson qubits.  相似文献   

9.
This paper reports that a quantum dense coding can be implemented with ions confined in a linear trap and interacting with laser beams. The scheme is insensitive to the interaction between the quantum channel and the environment. The Bell-state measurement is not involved and the probability of success in our scheme is 1.0.  相似文献   

10.
Individual laser-cooled 24Mg+ ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 microm above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.  相似文献   

11.
We theoretically investigated the mass dependence of the sympathetic cooling rate of gas-phase ions trapped in a linear radio-frequency-quadrupole ion trap. Using an a priori molecular dynamical calculation, tracing numerically with Newtonian equations of motion, we found that ions with a mass greater than 0.54±0.04 times that of the laser-cooled ions are sympathetically cooled; otherwise, they are heated. To understand the mass dependence obtained using the molecular-dynamical calculation, we made a heat-exchange model of sympathetic cooling, which shows that the factor of 0.54±0.04 is a consequence of absence of micro-motion along the axis of the linear ion trap. Received: 10 December 2001 / Revised version: 28 January 2002 / Published online: 14 March 2002  相似文献   

12.
An attempt is described to confine ions, created externally and accelerated to some energy, in an rf quadrupole trap. 4 keV Ba+ ions were stopped on a Ni foil, placed in an aperture of one trap electrode. The Ba then was evaporated from the heated foil and ionized by electron impact. At background pressure of about 10–5 mbar of various light buffer gases (He, H2, N2), the trap was filled once with 105 ions, at a minimum primary ion number of 1010. The storage time was 10 min. From the data obtained the possibility of spectroseopic experiments on rare isotopes, created with accelerators or nuclear reactors, is discussed.  相似文献   

13.
Cooled positive barium ions, proposed for new frequency standards, cease scattering cooling radiation for anomalously long periods in the presence of carbon dioxide or water. The probable mechanism is the attraction of a gas molecule to the ion as a result of the dipole induced in the molecule by the ion, followed by the formation of a weak chemical bond between the two. The mechanism seems applicable to any ion.  相似文献   

14.
The Wigner-Araki-Yanase theorem shows that conservation laws limit the accuracy of measurement. Here, we generalize the argument to show that conservation laws limit the accuracy of quantum logic operations. A rigorous lower bound is obtained of the error probability of any physical realization of the controlled-NOT gate under the constraint that the computational basis is represented by a component of spin, and that physical implementations obey the angular momentum conservation law. The lower bound is shown to be inversely proportional to the number of ancilla qubits or the strength of the external control field.  相似文献   

15.
We propose to use a single mesoscopic ensemble of trapped polar molecules for quantum computing. A "holographic quantum register" with hundreds of qubits is encoded in collective excitations with definite spatial phase variations. Each phase pattern is uniquely addressed by optical Raman processes with classical optical fields, while one- and two-qubit gates and qubit readout are accomplished by transferring the qubit states to a stripline microwave cavity field and a Cooper pair box where controllable two-level unitary dynamics and detection is governed by classical microwave fields.  相似文献   

16.
17.
We present experimental data on the state-selective quantum interference between different pathways of photorecombination, namely, radiative and dielectronic recombination, in the KLL resonances of highly charged mercury ions. The interference, observed for well resolved electronic states in the Heidelberg electron beam ion trap, manifests itself in the asymmetry of line shapes, characterized by "Fano factors," which have been determined with unprecedented precision, as well as their excitation energies, for several strong dielectronic resonances.  相似文献   

18.
A technique is proposed for injection-seeding control of tunable lasers. It is based on a combination of successive external injection and intracavity self-injection of radiation when the active medium is pumped by dual-step pulses. The technique is tested both experimentally (in the case of Nd:YAG-laser-pumped pulsed dye lasers) and numerically, using a model developed by us. Full conversion of the broadband spectrum into the injected line is achieved for an output energy greater by a factor of about 50 than that managed by means of the traditional injection-seeding technique under identical conditions.  相似文献   

19.
In this work.highly charged ions have been extracted from the advanced Electron Beam Ion Source (EBIS-A) developed in a scientific cooperation between the Dresden University of Technology and the DREEBIT GmbH Dresden.The charge state distributions of ions extracted from the EBIS-A are measured in and extracted in the leaky mode.3×105 Ar18+ ions per pulse are extracted in the pulse mode.The ion charge state distribution is a function of the ionization time.  相似文献   

20.
This paper proposes an experimentally feasible scheme for implementing quantum dense coding of trapped-ion system in decoherence-free states. As the phase changes due to time evolution of components with different eigenenergies of quantum superposition are completely frozen, quantum dense coding based on this model would be perfect. The scheme is insensitive to heating of vibrational mode and Bell states can be exactly distinguished via detecting the ionic state.  相似文献   

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