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Sep 19, 2013
09/13

by
Y. Y. Xu; W. L. Yang; M. Feng

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We investigate the dissipative dynamics of quantum discord in a decoherence model with two initially entangled qubits in addition to a quantum kicked top. The two qubits are uncoupled during the period of our study and one of them interacts with the quantum kicked top. We find that the long time behavior of quantum discord could be well described by the fidelity decay of the quantum kicked top; for short time behavior, however, the phase of the amplitude of the fidelity decay is necessary to...

Source: http://arxiv.org/abs/1010.3789v1

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Sep 18, 2013
09/13

by
W. L. Yang; C. Y. Chen; M. Feng

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Using resonant interaction of three Rydberg atoms with a single-mode microwave cavity, we consider a realization of three-qubit Grover search algorithm in the presence of weak cavity decay, based on a previous idea for three-qubit quantum gate [Phys. Rev. A 73, 064304 (2006)]. We simulate the searching process under the influence of the cavity decay and show that our scheme could be achieved efficiently to find the marked state with high fidelity. The required operations are very close to the...

Source: http://arxiv.org/abs/0707.0334v1

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Sep 19, 2013
09/13

by
W. L. Yang; Z. Y. Xu; M. Feng; J. F. Du

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We present a quantum electrodynamical model involving nitrogen-vacancy centers coupled to a whispering-gallery mode cavity. Two schemes are considered to create W state and Bell state, respectively. One of the schemes makes use of the Raman transition with the cavity field virtually excited; The other enables the Bell state preparation and quantum information transfer by virtue of dark state evolution and adiabatic passage, which is tolerant to ambient noise and experimental parameter...

Source: http://arxiv.org/abs/1010.3959v1

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Sep 18, 2013
09/13

by
T. Liu; M. Feng; W. L. Yang; J. H. Zou; L. Li; Y. X. Fan; K. L. Wang

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The light-matter interaction described by Rabi model and Jaynes-Cummings (JC) model is investigated by parity breaking as well as the scaling behavior of ground-state population-inversion expectation. We show that the parity breaking leads to different scaling behaviors in the two models, where the Rabi model demonstrates scaling invariance, but the JC model behaves in cusp-like way. Our study helps further understanding rotating-wave approximation and could present more subtle physics than any...

Source: http://arxiv.org/abs/1211.4202v2

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3.0

Jun 30, 2018
06/18

by
X. M. Feng; G. R. Jin; W. Yang

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Optimal measurement scheme with an efficient data processing is important in quantum-enhanced interferometry. Here we prove that for a general binary outcome measurement, the simplest data processing based on inverting the average signal can saturate the Cram\'{e}r-Rao bound. This idea is illustrated by binary outcome homodyne detection, even-odd photon counting (i.e., parity detection), and zero-nonzero photon counting that have achieved super-resolved interferometric fringe and shot-noise...

Topics: Quantum Physics, Physics, Optics

Source: http://arxiv.org/abs/1404.1229

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Sep 21, 2013
09/13

by
H. Q. Fan; W. L. Yang; X. R. Huang; M. Feng

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We study the possibility of an implementation of N-qubit (N>3) Grover search in cavity QED, based on a fast operation of N-qubit controlled phase-flip with atoms in resonance with the cavity mode. We demonstrate both analytically and numerically that, our scheme could be achieved efficiently to find a marked state with high fidelity and high success probability. As cavity decay is involved in our quantum trajectory treatment, we could analytically understand the implementation of a Grover...

Source: http://arxiv.org/abs/0808.2874v2

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Sep 21, 2013
09/13

by
T. Liu; K. L. Wang; M. Feng

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The single-mode spin-boson model (SMSBM) has extensive application in different subfields of physics. In the absence of rotating-wave approximation (RWA), we try to solve SMSBM analytically. We argue that the analytical expression obtained is the most exact approximation to the solution of the system under the assumption of Abel-Ruffini theorem, which works for a wide range of the parameters such as coupling strength and detuning and would be practical for currently available experiments.

Source: http://arxiv.org/abs/0905.0426v1

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3.0

Jun 30, 2018
06/18

by
G. Moody; M. Feng; C. McDonald; R. P. Mirin; K. L. Silverman

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In semiconductor quantum dots, the electron hyperfine interaction with the nuclear spin bath is the leading source of spin decoherence at cryogenic temperature. Using high-resolution two-color differential transmission spectroscopy, we demonstrate that such electron-nuclear coupling also imposes a lower limit for the positively charged exciton dephasing rate, \gamma, in an ensemble of InAs/GaAs quantum dots. We find that the dephasing rate is sensitive to the strength of the hyperfine...

Topics: Mesoscale and Nanoscale Physics, Condensed Matter

Source: http://arxiv.org/abs/1409.8354

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2.0

Jun 29, 2018
06/18

by
Y. Liu; J. K. Bao; H. K. Zuo; A. Ablimit; Z. T. Tang; C. M. Feng; Z. W. Zhu; G. H. Cao

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Impurity scattering in a superconductor may serve as an important probe for the nature of superconducting pairing state. Here we report the impurity effect on superconducting transition temperature $T_\mathrm{c}$ in the newly discovered Cr-based superconductor K$_2$Cr$_3$As$_3$. The resistivity measurements show that the crystals prepared using high-purity Cr metal ($\geq$99.99\%) have an electron mean free path much larger than the superconducting coherence length. For the crystals prepared...

Topics: Superconductivity, Condensed Matter

Source: http://arxiv.org/abs/1601.00824

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Sep 23, 2013
09/13

by
X. L. Zhang; M. Feng; K. L. Gao

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We investigate how to carry out universal quantum computation deterministically with free electrons in decoherence-free subspace by using polarizing beam splitters, charge detectors, and single-spin rotations. Quantum information in our case is encoded in spin degrees of freedom of the electron-pairs which construct a decoherence-free subspace. We design building blocks for two noncommutable single-logic-qubit gates and a logic controlled phase gate, based on which a universal and scalable...

Source: http://arxiv.org/abs/0710.3996v1

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2.0

Jun 30, 2018
06/18

by
Q. Wang; W. L. Yang; T. Liu; M. Feng; K. L. Wang

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We explore the possibility to generate new parity symmetry in the quantum Rabi model after a bias is introduced. In contrast to a mathematical treatment in a previous publication [J. Phys. A 46, 265302 (2013)], we consider a physically realistic method by involving an additional spin into the quantum Rabi model to couple with the original spin by an Ising interaction. The rule can be found that the parity symmetry is broken by introducing a bias and then restored by adding new degrees of...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1404.6918

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Sep 22, 2013
09/13

by
W. L. Yang; H. Wei; F. Zhou; W. L. Chang; M. Feng

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The main idea in the original Grover search (Phys. Rev. Lett. 79, 325 (1997)) is to single out a target state containing the solution to a search problem by amplifying the amplitude of the state, following the Oracle's job, i.e., a black box giving us information about the target state. We design quantum circuits to accomplish a complete Grover search involving both the Oracle's job and the amplification of the target state, which are employed to solve Satisfiability (SAT) problems. We explore...

Source: http://arxiv.org/abs/0811.2905v1

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Sep 20, 2013
09/13

by
X. L. Zhang; K. L. Gao; M. Feng

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We propose schemes to create cluster states and W states by many superconducting-quantum-interference-device (SQUID) qubits in cavities under the influence of the cavity decay. Our schemes do not require auxiliary qubits, and the excited levels are only virtually coupled throughout the scheme, which could much reduce the experimental challenge. We consider the cavity decay in our model and analytically demonstrate its detrimental influence on the prepared entangled states.

Source: http://arxiv.org/abs/quant-ph/0608111v1

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Sep 21, 2013
09/13

by
W. L. Yang; Zhang-qi Yin; Y. Hu; M. Feng; J. F. Du

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We study a hybrid quantum computing system using nitrogen-vacancy center ensemble (NVE) as quantum memory, current-biased Josephson junction (CBJJ) superconducting qubit fabricated in a transmission line resonator (TLR) as quantum computing processor and the microwave photons in TLR as quantum data bus. The storage process is seriously treated by considering all kinds of decoherence mechanisms. Such a hybrid quantum device can also be used to create multi-qubit W states of NVEs through a common...

Source: http://arxiv.org/abs/1106.2909v1

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Sep 17, 2013
09/13

by
Z. Y. Xu; W. L. Yang; M. Feng

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The non-Markovianity is a recently proposed characterization of the non-Markovian behavior in an open quantum system, based on which we first present a practical idea for directly measuring the non-Markovian character of a single qubit coupled to a zero-temperature bosonic reservoir, and then extend to investigate the dynamics of two noninteracting qubits subject to two reservoirs respectively with a lower bound of non-Markovianity. Our scheme, with no need of optimization procedures and...

Source: http://arxiv.org/abs/0912.2879v4

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Sep 21, 2013
09/13

by
W. L. Yang; Zhang-qi Yin; Z. X. Chen; Su-Peng Kou; M. Feng; C. H. Oh

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We propose a potentially practical scheme to simulate artificial Abelian gauge field for polaritons using a hybrid quantum system consisting of nitrogen-vacancy center ensembles (NVEs) and superconducting transmission line resonators (TLR). In our case, the collective excitations of NVEs play the role of bosonic particles, and our multiport device tends to circulate polaritons in a behavior like a charged particle in an external magnetic field. We discuss the possibility of identifying...

Source: http://arxiv.org/abs/1204.1778v1

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57

Sep 19, 2013
09/13

by
Z. J. Deng; M. Feng; K. L Gao

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By means of the Ising terms generated by Coulomb interaction between ions and the magnetic field gradient, we carry out teleportation with insurance with trapped ions. We show the feasibility and the favorable feature of our scheme by comparing with the recently achieved teleportation experiments with trapped ions.

Source: http://arxiv.org/abs/quant-ph/0507080v1

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Sep 20, 2013
09/13

by
X. L. Zhang; M. Feng; K. L. Gao

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A potential scheme is proposed to generate complete sets of entangled photons in the context of cavity quantum electrodynamics (QED). The scheme includes twice interactions of atoms with cavities, in which the first interaction is made in two-mode optical cavities and the second one exists in a microwave cavity. In the optical cavities the atoms are resonant with the cavity modes, while the detuned interaction of the atoms with a single-mode of the microwave cavity is driven by a classical...

Source: http://arxiv.org/abs/quant-ph/0607090v1

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Sep 19, 2013
09/13

by
X. L. Zhang; K. L. Gao; M. Feng

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We propose a scheme to generate cluster states of atomic qubits by using cavity quantum electrodynamics (QED) and linear optics, in which each atom is confined in a resonant optical cavity with two orthogonally polarized modes. Our scheme is robust to imperfect factors such as dissipation, photon loss, and detector inefficiency. Discussions are made for experimental feasibility of our scheme.

Source: http://arxiv.org/abs/quant-ph/0703116v1

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53

Sep 18, 2013
09/13

by
T. Liu; K. L. Wang; M. Feng

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We consider a single ion confined in a trap under radiation of two traveling waves of lasers. In the strong-excitation regime and without the restriction of Lamb-Dicke limit, the Hamiltonian of the system is similar to a driving Jaynes-Cummings model without rotating wave approximation (RWA). The approach we developed enables us to present a complete eigensolutions, which makes it available to compare with the solutions under the RWA. We find that, the ground state in our non-RWA solution is...

Source: http://arxiv.org/abs/0704.0117v1

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Jul 20, 2013
07/13

by
Z. W. Zhu; Z. A. Xu; X. Lin; G. H. Cao; C. M. Feng; G. F. Chen; Z. Li; J. L. Luo; N. L. Wang

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We report the first Nernst effect measurement on the new iron-based superconductor LaO$_{1-x}$F$_{x}$FeAs $(x=0.1)$. In the normal state, the Nernst signal is negative and very small. Below $T_{c}$ a large positive peak caused by vortex motion is observed. The flux flowing regime is quite large compared to conventional type-II superconductors. However, a clear deviation of the Nernst signal from normal state background and an anomalous depression of off-diagonal thermoelectric current in the...

Source: http://arxiv.org/abs/0804.1324v2

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Sep 21, 2013
09/13

by
Jun-Hong An; M. Feng; C. H. Oh

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Both cavity QED and photons are promising candidates for quantum information processing. We consider a combination of both candidates with a single photon going through spatially separate cavities to entangle the atomic qubits, based on the input-output process of the cavities. We present a general expression for the input-output process regarding the low-Q cavity confining a single atom, which works in a wide range of parameters. Focusing on low-Q cavity case, we propose some schemes for...

Source: http://arxiv.org/abs/0902.1372v1

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Sep 23, 2013
09/13

by
M. Feng; Y. Y. Xu; F. Zhou; D. Suter

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Physical systems must fulfill a number of conditions to qualify as useful quantum bits (qubits) for quantum information processing, including ease of manipulation, long decoherence times, and high fidelity readout operations. Since these conditions are hard to satisfy with a single system, it may be necessary to combine different degrees of freedom. Here we discuss a possible system, based on electronic and nuclear spin degrees of freedom in trapped ions. The nuclear spin yields long...

Source: http://arxiv.org/abs/0904.4020v1

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Sep 21, 2013
09/13

by
W. L. Yang; Jun-Hong An; Chengjie Zhang; M. Feng; C. H. Oh

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We investigate the non-Markovian dynamics of quantum correlation between two initially entangled nitrogen-vacancy centers (NVC) embedded in photonic crystal cavities (PCC). We find that a finite quantum correlation is preserved even asymptotically when the transition frequency of the NVC is within the band gap of the PCC, which is quantitatively different from the result of approaching zero under the Born-Markovian approximation. In addition, once the transition frequency of NVC is far beyond...

Source: http://arxiv.org/abs/1301.7494v2

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Sep 21, 2013
09/13

by
M. Feng; J. Twamley

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We propose two potentially practical schemes to carry out two-qubit quantum gates on endohedral fullerenes $N@C_{60}$ or $P@C_{60}$. The qubits are stored in electronic spin degrees of freedom of the doped atom $N$ or $P$. By means of the magnetic dipolar coupling between two neighboring fullerenes, the two-qubit controlled-NOT gate and the two-qubit conditional phase gate are performed by selective microwave pulses assisted by refocusing technique. We will discuss the necessary additional...

Source: http://arxiv.org/abs/quant-ph/0311178v2

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Jul 20, 2013
07/13

by
Zhang-qi Yin; Tongcang Li; M. Feng

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We propose an experimental scheme to cool and measure the three-dimensional (3D) motion of an optically trapped nanosphere in a cavity. Driven by three lasers on TEM00, TEM01, and TEM10 modes, a single cavity can cool a trapped nanosphere to the quantum ground states in all three dimensions under the resolved-sideband condition. Our scheme can also detect an individual collision between a single molecule and a cooled nanosphere efficiently. Such ability can be used to measure the mass of...

Source: http://arxiv.org/abs/1007.0827v2

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Jul 19, 2013
07/13

by
Z. Y. Xu; M. Feng

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We investigate how to effectively preserve the entanglement between two noninteracting multilevel oscillators coupled to a common reservoir under non-ideal pulse control. A universal characterization using fidelity is developed for the behavior of the system based on Nakajima-Zwanzig projection operator technique. Our analysis includes the validity of the approximation method and the decoherence-suppression by the non-ideal pulse control. The power of our strategy for protecting entanglement is...

Source: http://arxiv.org/abs/1005.3171v1

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Sep 18, 2013
09/13

by
M. Feng; Z. J. Deng; K. L. Gao

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We propose a potential scheme to generate entangled photons by manipulating trapped ions embedded in two-mode microcavities, respectively, assisted by a magnetic field gradient. By means of the spin-spin coupling due to the magnetic field gradient and the Coulomb repulsion between the ions, we show how to efficiently generate entangled photons by detecting the internal states of the trapped ions. We emphasize that our scheme is advantageous to create complete sets of entangled multi-photon...

Source: http://arxiv.org/abs/quant-ph/0509138v1

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Sep 23, 2013
09/13

by
Z. Y. Xu; M. Feng

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We investigate the entanglement dynamics of two initially entangled qubits interacting independently with two uncorrelated reservoirs beyond the Markovian approximation. Quite different from the Markovian reservoirs [C. E. Lopez et al., Phys. Rev. Lett. 101 (2008) 080503], we find that entanglement sudden birth (ESB) of the two reservoirs occurs without certain symmetry with respect to the entanglement sudden death (ESD) of the two qubits. A phenomenological interpretation of entanglement...

Source: http://arxiv.org/abs/0903.4225v2

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4.0

Jun 30, 2018
06/18

by
M. Feng; Y. P. Zhong; T. Liu; L. L. Yan; W. L. Yang; J. Twamley; H. Wang

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Quantum phase transitions play an important role in many-body systems and have been a research focus in conventional condensed matter physics over the past few decades. Artificial atoms, such as superconducting qubits that can be individually manipulated, provide a new paradigm of realising and exploring quantum phase transitions by engineering an on-chip quantum simulator. Here we demonstrate experimentally the quantum critical behaviour in a highly-controllable superconducting circuit,...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1406.1436

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45

Sep 23, 2013
09/13

by
Z. Y. Xu; M. Feng; W. M. Zhang

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We investigate the possibility to have electron-pairs in dephasing-free subspace (DFS), by means of the quantum-dot cellular automata (QCA) and single-spin rotations, to carry out a high-fidelity and deterministic universal quantum computation. We show that our QCA device with electrons tunneling two dimensionally is very suitable for DFS encoding, and argue that our design favors a scalable quantum computation robust to collective dephasing errors.

Source: http://arxiv.org/abs/0801.4617v2

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Jun 28, 2018
06/18

by
X. M. Feng; P. Wang; W. Yang; G. R. Jin

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The precise calculations of the Wigner's d-matrix are important in various research fields. Due to the presence of large numbers, direct calculations of the matrix using the Wigner's formula suffer from loss of precision. We present a simple method to avoid this problem by expanding the d-matrix into a complex Fourier series and calculate the Fourier coefficients by exactly diagonalizing the angular-momentum operator $J_{y}$ in the eigenbasis of $J_{z}$. This method allows us to compute the...

Topics: Quantum Physics, Mathematical Physics, Computational Physics, Physics, Atomic Physics, Nuclear...

Source: http://arxiv.org/abs/1507.04535

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Sep 20, 2013
09/13

by
Z. J. Deng; K. L. Gao; M. Feng

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A simple scheme is presented to generate n-qubit W state with rf-superconducting quantum interference devices (rf-SQUIDs) in cavity QED through adiabatic passage. Because of the achievable strong coupling for rf-SQUID qubits embedded in cavity QED, we can get the desired state with high success probability. Furthermore, the scheme is insensitive to position inaccuracy of the rf-SQUIDs. The numerical simulation shows that, by using present experimental techniques, we can achieve our scheme with...

Source: http://arxiv.org/abs/quant-ph/0612161v1

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Sep 24, 2013
09/13

by
M Feng; J Twamley

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Spin state detection is a key but very challenging step for any spin-based solid-state quantum computing technology. In fullerene based quantum computer technologies, we here propose to detect the single spin inside a fullerene by transferring the quantum information from the endohedral spin to the ground states of a molecular nanomagnet Fe$_{8}$, with large spin S=10. We show how to perform the required SWAP operation and how to read out the information through state-of-the-art techniques such...

Source: http://arxiv.org/abs/quant-ph/0412081v2

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42

Sep 19, 2013
09/13

by
Z. J. Deng; M. Feng; K. L. Gao

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Following the proposal by F. Yamaguchi et al.[Phys. Rev. A 66, 010302 (R) (2002)], we present an alternative way to implement the two-qubit Grover search algorithm in cavity QED. Compared with F. Yamaguchi et al.'s proposal, with a strong resonant classical field added, our method is insensitive to both the cavity decay and thermal field, and doesn't require that the cavity remain in the vacuum state throughout the procedure. Moreover, the qubit definitions are the same for both atoms, which...

Source: http://arxiv.org/abs/quant-ph/0507129v1

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Jun 15, 2020
06/20

by
M Feng; A M Waite; P A Thompson

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61

Jul 20, 2013
07/13

by
Z. Y. Xu; W. L. Yang; M. Feng

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The measurement outcomes of two incompatible observables on a particle can be precisely predicted when it is maximally entangled with a quantum memory, as quantified recently [Nature Phys. 6, 659 (2010)]. We explore the behavior of the uncertainty relation under the influence of local unital and nonunital noisy channels. While the unital noises only increase the amount of uncertainty, the amplitude-damping nonunital noises may amazingly reduce the amount of uncertainty in the long-time limit....

Source: http://arxiv.org/abs/1203.3331v1

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Sep 18, 2013
09/13

by
M. Feng; J. Twamley

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The readout of the quantum spin state is a challenge for any spin-based quantum computing implementation. We propose a scheme, based on the achieved technique of single electron transistor (SET), to implement the readout of electronic spin state inside a doped $C_{60}$ fullerene by means of the magnetic dipole-dipole coupling and spin filters. In the presence of an external magnetic field, we show how to perform the spin state detection by transforming the information contained in the spin...

Source: http://arxiv.org/abs/quant-ph/0401157v2

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Sep 20, 2013
09/13

by
T. T. Ren; M. Feng; W. -L. Chang; J. Luo; M. S. Zhan

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DNA computation could in principle solve the satisfiability (SAT) problem due to the operations in parallel on extremely large numbers of strands. We demonstrate some quantum gates corresponding to the DNA ones, based on which an implementation of DNA algorithm for SAT problem is available by quantum mechanical way. Since quantum computation owns the favorable feature of operations in parallel on 2$^{n}$ states by using only n qubits, instead of 2$^{n}$ strands in DNA computation, computational...

Source: http://arxiv.org/abs/0802.0232v1

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Sep 18, 2013
09/13

by
W. L. Yang; H. Wei; X. L. Zhang; M. Feng

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We propose a potentially practical scheme, in combination with the Bell-state analyzer [Zhang et al., Phys. Rev. A 73, 014301 (2006)], to generate Bell states for two electron spins confined, respectively, in two distant fullerenes. To this end, we consider the endohedral fullerenes staying in single walled carbon nanotubes (SWCNTs) and employ auxiliary mobile electrons and selective microwave pulses. The application and the experimental feasibility of our scheme are discussed.

Source: http://arxiv.org/abs/0809.3056v1

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Sep 20, 2013
09/13

by
J. Hooper; M. H. Fang; M. Zhou; D. Fobes; N. Dang; Z. Q. Mao; C. M. Feng; Z. A. Xu; M. H. Yu; C. J. OConnor; G. J. Xu; N. Andersen; M. Salamon

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We report the effect of nonmagnetic Ti4+ impurities on the electronic and magnetic properties of Sr3Ru2O7. Small amounts of Ti suppress the characteristic peak in magnetic susceptibility near 16 K and result in a sharp upturn in specific heat. The metamagnetic quantum phase transition and related anomalous features are quickly smeared out by small amounts of Ti. These results provide strong evidence for the existence of competing magnetic fluctuations in the ground state of Sr3Ru2O7. Ti doping...

Source: http://arxiv.org/abs/cond-mat/0607414v2

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Sep 18, 2013
09/13

by
T. Liu; M. Feng; K. L. Wang

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The quantum behavior of a precooled cantilever can be probed highly efficiently by coupling to a trapped ultracold ion, in which a fast cooling of the cantilever down to the ground vibrational state is possible. We solve the dynamics of the coupling system by a squeezed-state expansion technique, and can in principle obtain the exact solution of the time-evolution of the coupling system. Compared to the treatment under rotating-wave approximation, we can present a more accurate description of...

Source: http://arxiv.org/abs/quant-ph/0509160v2

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Sep 19, 2013
09/13

by
M. Feng; G. J. Dong; B. Hu

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We consider to detect the electron spin of a doped atom, i.e., a nitrogen or a phosphorus, caged in a fullerene by currently available technique of the scanning tunneling microscope (STM), which actually corresponds to the readout of a qubit in the fullerene-based quantum computing. Under the conditions of polarized STM current and Coulomb blockade, we investigate the tunneling matrix elements involving the exchange coupling between the tunneling polarized electrons and the encapsulated...

Source: http://arxiv.org/abs/quant-ph/0610083v1