共查询到20条相似文献,搜索用时 15 毫秒
1.
文章介绍了作者用介观输运器件[如量子点接触(QPC)或单电子晶体管(SET)]测量固态量子比特的原理和特性, 特别着重地介绍了作者最近在处理被测量子比特和介观测量仪器之间的关联方面的新进展. 相似文献
2.
文章介绍了作者用介观输运器件[如量子点接触(QPC)或单电子晶体管(SET)]测量固态量子比特的原理和特性,特别着重地介绍了作者最近在处理被测量子比特和介观测量仪器之间的关联方面的新进展。 相似文献
3.
We present the measurement of a hybrid double-dot qubit using a quantum point contact (QPC). To study the dy- namics, we derive the rate equations of the entire system. Numerical results show that QPC current can directly reflect the evolution of the qubit. By adjusting Coulomb interaction, energy mismatch, and QPC tunneling rate, the efficiency and dephasing time can be improved. In addition, the initial state with a hybrid triplet state is superior to that with the purely triplet states on the efficiency. Moreover, the decoherence time is estimated on the magnitude of a microsecond, long enough to implement quantum operations. 相似文献
4.
We report on the application of a dynamic decoherence control pulse sequence on a nuclear-quadrupole transition in Pr3+:Y(2)SiO(5). Process tomography is used to analyze the effect of the pulse sequence. The pulse sequence was found to increase the decoherence time of the transition to over 30 seconds. Although the decoherence time was significantly increased, the population terms were found to rapidly decay on the application of the pulse sequence. The increase of this decay rate is attributed to inhomogeneity in the ensemble. Methods to circumvent this limit are discussed. 相似文献
5.
《中国光学快报(英文版)》2017,(5)
We show how to optimally protect quantum states and freeze coherence under incoherent channels using a quantum weak measurement and quantum measurement reversal. In particular, we present explicit formulas for the conditions for freezing quantum coherence in a given quantum state. 相似文献
6.
The remote implementation of all possible generalized quantum measurement on single atomic qubit in a quantum network
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)
To implement generalized quantum measurement (GQM) one has to extend
the original Hilbert space. Generally speaking, the additional
dimensions of the ancilla space increase as the number of the
operators of the GQM n increases. This paper presents a scheme for
deterministically implementing all possible n-operator GQMs on a
single atomic qubit by using only one 2-dimensional ancillary atomic
qubit repeatedly, which remarkably reduces the complexity of the
realistic physical system. Here the qubit is encoded in the internal states
of an atom trapped in an optical cavity and single-photon pulses are
employed to provide the interaction between qubits. It shows that
the scheme can be performed remotely, and thus it is suitable for
implementing GQM in a quantum network. What is more, the number of the
total ancilla dimensions in our scheme achieves the theoretic low
bound. 相似文献
7.
Amplifying and freezing of quantum coherence using weak measurement and quantum measurement reversal
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 analyze universal conditions where the l_1 norm and relative entropy of coherence are amplified and frozen under identical bit-flip channels;that is,using pre-measurements(quantum weak measurements or quantum measurement reversals) on the systems before undergoing local bit-flip channels.With the option of quantum weak measurements or quantum measurement reversals,the measurement strength and the success probability are all determined by the initial state of the quantum system. 相似文献
8.
In this paper, we propose a scheme to enhance trapping of entanglement of two qubits in the environment of a photonic band gap material. Our entanglement trapping promotion scheme makes use of combined weak measurements and quantum measurement reversals. The optimal promotion of entanglement trapping can be acquired with a reasonable finite success probability by adjusting measurement strengths. 相似文献
9.
Recent work by Lundeen et al. [Nature (London) 474, 188 (2011)] directly measured the wave function by weakly measuring a variable followed by a normal (i.e., "strong") measurement of the complementary variable. We generalize this method to mixed states by considering the weak measurement of various products of these observables, thereby providing the density matrix an operational definition in terms of a procedure for its direct measurement. The method only requires measurements in two bases and can be performed in situ, determining the quantum state without destroying it. 相似文献
10.
We study the asymptotic dynamics of a driven spin-boson system
where the environment is formed by a broadened localized mode.
Upon exploiting an exact mapping, an equivalent formulation of the
problem in terms of a quantum two-state system (qubit) coupled to
a harmonic oscillator which is itself Ohmically damped, is found.
We calculate the asymptotic population difference of the two
states in two complementary parameter regimes. For weak damping
and low temperature, a perturbative Floquet-Born-Markovian master
equation for the qubit-oscillator system can be solved. We find
multi-photon resonances corresponding to transitions in the
coupled quantum system and calculate their line-shape
analytically. In the complementary parameter regime of strong
damping and/or high temperatures, non-perturbative real-time path
integral techniques yield analytic results for the resonance line
shape. In both regimes, we find very good agreement with exact
results obtained from a numerical real-time path-integral
approach. Finally, we show for the case of strong detuning between
qubit and oscillator that the width of the n-photon resonance
scales with the nth Bessel function of the driving strength in
the weak-damping regime. 相似文献
11.
Multipartite quantum correlations are important resources for the development of quantum information and computation protocols. However, the resourcefulness of multipartite quantum correlations in practical settings is limited by its fragility under decoherence due to environmental interactions. Though there exist protocols to protect bipartite entanglement under decoherence, the implementation of such protocols for multipartite quantum correlations has not been sufficiently explored. Here, we study the effect of local amplitude damping channel on the generalized Greenberger–Horne–Zeilinger state, and use a protocol of optimal reversal quantum weak measurement to protect the multipartite quantum correlations. We observe that the weak measurement reversal protocol enhances the robustness of multipartite quantum correlations. Further it increases the critical damping value that corresponds to entanglement sudden death. To emphasize the efficacy of the technique in protection of multipartite quantum correlation, we investigate two proximately related quantum communication tasks, namely, quantum teleportation in a one sender, many receivers setting and multiparty quantum information splitting, through a local amplitude damping channel. We observe an increase in the average fidelity of both the quantum communication tasks under the weak measurement reversal protocol. The method may prove beneficial, for combating external interactions, in other quantum information tasks using multipartite resources. 相似文献
12.
We analyze the dynamics of a continuously observed, damped, microwave-driven solid state charge qubit, consisting of a single electron in a double well potential. The microwave field induces transitions between the qubit eigenstates, which have a profound effect on the detector output current. Useful information about the qubit dynamics, such as dephasing and relaxation rates, and the Rabi frequency, can be extracted from the detector conductance and output noise power spectrum. We also propose a technique for single-shot electron spin readout, for spin based quantum information processing, which has a number of practical advantages over existing schemes. 相似文献
13.
Quantum phase transitions occur when the ground state of a quantum system undergoes a qualitative change when an external control parameter reaches a critical value. Here, we demonstrate a technique for studying quantum systems undergoing a phase transition by coupling the system to a probe qubit. It uses directly the increased sensibility of the quantum system to perturbations when it is close to a critical point. Using an NMR quantum simulator, we demonstrate this measurement technique for two different types of quantum phase transitions in an Ising spin chain. 相似文献
14.
A terahertz (THz) microspectroscope is developed, in which the frequency of extremely weak THz radiation is resolved by scanning the magnetic field for a quantum Hall detector. The electron density of the detectors is controlled by the back-gate biasing, so that the detector sensitivity is calibrated over a spectral range studied. Reliable spectral measurements with a spectral resolution of 1.2 cm−1 has been made with a sensitivity better than 10 femtowatt level over 1 s integration time. 相似文献
15.
Enhancing the precision of phase estimation by weak measurement and quantum measurement reversal
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)
The enhancement of the precision of phase estimation in quantum metrology is investigated by employing weak measurement (WM) and quantum measurement reversal (QMR). We derive the exact expressions of the optimal quantum Fisher information (QFI) and success probability of phase estimation for an exactly solving model consisting of a qubit interacting with a structured reservoir. We show that the QFI can be obviously enhanced by means of the WM and QMR in different regimes. In addition, we also show that the magnitude of the decoherence involved in the WM and QMR can be a general complex number, which extends the applicable scope of the WM and QMR approach. 相似文献
16.
We study the eigenenergies and the eigenfunctions of the ground and the first excited states of an electron, which is strongly coupled to LO-phonon in a quantum rod with a hydrogen-like impurity at the center by using the variational method of Pekar type. This quantum rod system may be used as a two-level quantum qubit. When the electron is in the superposition state of the ground and the first-excited states, the probability density of the electron oscillates in the quantum rod. It is found that the probability density and the oscillation period are individually increased and decreased due to the presence of the Coulomb interaction between the electron and the hydrogen-like impurity. The oscillation period is an increasing function of the ellipsoid aspect ratio and the effective confinement lengths of the quantum rod, whereas it is a decreasing one of the electron–phonon coupling strength. 相似文献
17.
Wang Y. D. Gao Y. B. Sun C. P. 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,40(3):321-326
We propose a theoretical scheme to observe the loss of quantum coherence through the coupling of the superconducting charge qubit system to a nanomechanical resonator (NAMR), which has already been successfully fabricated in experiment and is convenient to manipulate. With a similar form to the usual cavity QED system, this qubit-NAMR composite system with engineered coupling exhibits the collapse and revival phenomenon in a progressive decoherence process. Corresponding to the two components of superposition of the two charge eigenstates, the state of the nanomechanical resonator evolves simultaneously towards two distinct quasi-classical states. Therefore the generalized which way detection by the NAMR induces the quantum decoherence of the charge qubit.Received: 21 May 2004, Published online: 9 September 2004PACS:
03.65.-w Quantum mechanics - 74.50. + r Tunneling phenomena; point contacts, weak links, Josephson effects - 03.67.Lx Quantum computation - 85.25.Dq Superconducting quantum interference devices (SQUIDs) 相似文献
18.
In this work we first derive a generalized conditional master equation for quantum measurement by a mesoscopic detector, then study the readout characteristics of qubit measurement where a number of remarkable new features are found. The work would, in particular, highlight the qubit spontaneous relaxation effect induced by the measurement itself rather than an external thermal bath. 相似文献
19.
20.
Schmid C Trojek P Bourennane M Kurtsiefer C Zukowski M Weinfurter H 《Physical review letters》2005,95(23):230505
We present a simple and practical protocol for the solution of a secure multiparty communication task, the secret sharing, and its proof-of-principle experimental realization. In this protocol, a secret is split among several parties in a way that its reconstruction requires the collaboration of the participating parties. In our scheme the parties solve the problem by sequential transformations on a single qubit. In contrast with recently proposed schemes involving multiparticle Greenberger-Horne-Zeilinger states, the approach demonstrated here is much easier to realize and scalable in practical applications. 相似文献