Virtual Journal of Quantum Information
Imaging a one-electron InAs quantum dot in an InAs/InP nanowire
Ania C. Bleszynski-Jayich, Linus E. Froberg, Mikael T. Bjork, H. J. Trodahl, Lars Samuelson et al.
Nanowire heterostructures define high-quality few-electron quantum dots for nanoelectronics, spintronics, and quantum information processing. We use a cooled scanning probe microscope (SPM) to image and control an InAs quantum dot in an InAs/InP nanowire using the tip as a movable gate. Images of do ... [Phys. Rev. B 77, 245327 (2008)] published Mon Jun 30, 2008.
Nanowire heterostructures define high-quality few-electron quantum dots for nanoelectronics, spintronics, and quantum information processing. We use a cooled scanning probe microscope (SPM) to image and control an InAs quantum dot in an InAs/InP nanowire using the tip as a movable gate. Images of do ... [Phys. Rev. B 77, 245327 (2008)] published Mon Jun 30, 2008.
Tm[sup 3+]:Y[sub 2]O[sub 3] investigated for a quantum light storage application
T. Chaneliere, J. Ruggiero, J.-L. Le Gouet, W. Tittel, J.-H. Mun et al.
In this paper, we investigate a new medium for quantum light storage in crystals. Indeed, Tm:YO exhibits all the features that are currently considered crucial for a storage protocol. First, optical measurements confirm our crystal-field analysis. Then, we explain how to tailor a three-level Lambda ... [Phys. Rev. B 77, 245127 (2008)] published Fri Jun 20, 2008.
In this paper, we investigate a new medium for quantum light storage in crystals. Indeed, Tm:YO exhibits all the features that are currently considered crucial for a storage protocol. First, optical measurements confirm our crystal-field analysis. Then, we explain how to tailor a three-level Lambda ... [Phys. Rev. B 77, 245127 (2008)] published Fri Jun 20, 2008.
Spin-dependent processes at the crystalline Si-SiO[sub 2] interface at high magnetic fields
D. R. McCamey, G. W. Morley, H. A. Seipel, L. C. Brunel, J. van Tol et al.
An experimental study on the nature of spin-dependent excess charge-carrier transitions at the interface between (111)-oriented phosphorous-doped ([P][approximate]10 cm) crystalline silicon and silicon dioxide at high magnetic field (B[approximate]8.5 T) is presented. Electrically detected magneti ... [Phys. Rev. B 78, 045303 (2008)] published Wed Jul 2, 2008.
An experimental study on the nature of spin-dependent excess charge-carrier transitions at the interface between (111)-oriented phosphorous-doped ([P][approximate]10 cm) crystalline silicon and silicon dioxide at high magnetic field (B[approximate]8.5 T) is presented. Electrically detected magneti ... [Phys. Rev. B 78, 045303 (2008)] published Wed Jul 2, 2008.
Single-photon transistor using microtoroidal resonators
Fang-Yu Hong and Shi-Jie Xiong
We present a scheme for single-photon transistors based on the strong interaction of a three-level atom with a microtoroidal resonator, where the presence (absence) of a single gate photon is sufficient to block (allow) the propagation of a signal photon. Considering its robustness against major exp ... [Phys. Rev. A 78, 013812 (2008)] published Wed Jul 9, 2008.
We present a scheme for single-photon transistors based on the strong interaction of a three-level atom with a microtoroidal resonator, where the presence (absence) of a single gate photon is sufficient to block (allow) the propagation of a signal photon. Considering its robustness against major exp ... [Phys. Rev. A 78, 013812 (2008)] published Wed Jul 9, 2008.
Quantum decoherence of a charge qubit in a spin-fermion model
Roman M. Lutchyn, Lukasz Cywinski, Cody P. Nave, and S. Das Sarma
We consider quantum decoherence in solid-state systems by studying the transverse dynamics of a single qubit interacting with a fermionic bath and driven by external pulses. Our interest is in investigating the extent to which the lost coherence can be restored by the application of external pulses ... [Phys. Rev. B 78, 024508 (2008)] published Wed Jul 9, 2008.
We consider quantum decoherence in solid-state systems by studying the transverse dynamics of a single qubit interacting with a fermionic bath and driven by external pulses. Our interest is in investigating the extent to which the lost coherence can be restored by the application of external pulses ... [Phys. Rev. B 78, 024508 (2008)] published Wed Jul 9, 2008.
High-Fidelity Gates in a Single Josephson Qubit
Erik Lucero, M. Hofheinz, M. Ansmann, Radoslaw C. Bialczak, N. Katz et al.
We demonstrate new experimental procedures for measuring small errors in a superconducting quantum bit (qubit). By carefully separating out gate and measurement errors, we construct a complete error budget and demonstrate single qubit gate fidelities of 0.98, limited by energy relaxation. We also in ... [Phys. Rev. Lett. 100, 247001 (2008)] published Mon Jun 16, 2008.
We demonstrate new experimental procedures for measuring small errors in a superconducting quantum bit (qubit). By carefully separating out gate and measurement errors, we construct a complete error budget and demonstrate single qubit gate fidelities of 0.98, limited by energy relaxation. We also in ... [Phys. Rev. Lett. 100, 247001 (2008)] published Mon Jun 16, 2008.
Spin and angular momentum transitions in few-electron quantum dots and rings
Ning Yang, Zhensheng Dai, and Jia-Lin Zhu
The studies on quantum dots and rings containing 4~6 electrons reveal that the shapes of the systems have great impact on the spin transitions of the ground states. For five-electron case, the different shapes lead to the different transition processes in quantum dots and rings. For six-electron cas ... [Phys. Rev. B 77, 245321 (2008)] published Mon Jun 23, 2008.
The studies on quantum dots and rings containing 4~6 electrons reveal that the shapes of the systems have great impact on the spin transitions of the ground states. For five-electron case, the different shapes lead to the different transition processes in quantum dots and rings. For six-electron cas ... [Phys. Rev. B 77, 245321 (2008)] published Mon Jun 23, 2008.
Phase diagram for condensation of microcavity polaritons: From theory to practice
F. M. Marchetti, M. H. Szymanska, J. M. J. Keeling, J. Kasprzak, R. Andre et al.
The first realization of a polariton condensate was recently achieved in a CdTe microcavity [Kasprzak et al., Nature (London) 443, 409 (2006)]. We compare the experimental phase boundaries, for various detunings and cryostat temperatures, with those found theoretically from a model which accounts fo ... [Phys. Rev. B 77, 235313 (2008)] published Thu Jun 19, 2008.
The first realization of a polariton condensate was recently achieved in a CdTe microcavity [Kasprzak et al., Nature (London) 443, 409 (2006)]. We compare the experimental phase boundaries, for various detunings and cryostat temperatures, with those found theoretically from a model which accounts fo ... [Phys. Rev. B 77, 235313 (2008)] published Thu Jun 19, 2008.
Nonlocal dispersion control of a single-photon waveform
So-Young Baek, Osung Kwon, and Yoon-Ho Kim
We demonstrate explicitly that a single-photon waveform, conditionally prepared by detecting the trigger photon of the photon pair born in the process of spontaneous parametric down-conversion, becomes broadened and chirped as the result of propagation through a single-mode optical fiber. The pulsel ... [Phys. Rev. A 78, 013816 (2008)] published Thu Jul 10, 2008.
We demonstrate explicitly that a single-photon waveform, conditionally prepared by detecting the trigger photon of the photon pair born in the process of spontaneous parametric down-conversion, becomes broadened and chirped as the result of propagation through a single-mode optical fiber. The pulsel ... [Phys. Rev. A 78, 013816 (2008)] published Thu Jul 10, 2008.
Creation of cluster states of trapped ions by collective addressing
Peter A. Ivanov, Nikolay V. Vitanov, and Martin B. Plenio
We propose an efficient technique for creation of cluster states of trapped ions. The ions are addressed collectively, in only two interaction steps, by a pair of pulses tuned near the blue- and red-sideband transitions. The technique is very suitable for four-ion cluster states, for which the initi ... [Phys. Rev. A 78, 012323 (2008)] published Mon Jul 14, 2008.
We propose an efficient technique for creation of cluster states of trapped ions. The ions are addressed collectively, in only two interaction steps, by a pair of pulses tuned near the blue- and red-sideband transitions. The technique is very suitable for four-ion cluster states, for which the initi ... [Phys. Rev. A 78, 012323 (2008)] published Mon Jul 14, 2008.
Analysis of experimental feasibility of polar-molecule-based phase gates
Elena Kuznetsova, Robin Cote, Kate Kirby, and S. F. Yelin
We analyze a recently proposed physical implementation of a quantum computer based on polar molecules with switchable dipoles, i.e., dipole moments that can be switched on and off. Conditional dipole-dipole interaction is an efficient tool for realizing two-qubit quantum gates necessary to construct ... [Phys. Rev. A 78, 012313 (2008)] published Wed Jul 9, 2008.
We analyze a recently proposed physical implementation of a quantum computer based on polar molecules with switchable dipoles, i.e., dipole moments that can be switched on and off. Conditional dipole-dipole interaction is an efficient tool for realizing two-qubit quantum gates necessary to construct ... [Phys. Rev. A 78, 012313 (2008)] published Wed Jul 9, 2008.
Methods for a linear optical quantum Fredkin gate
Yan-Xiao Gong, Guang-Can Guo, and Timothy C. Ralph
We consider the realization of a quantum Fredkin gate with only linear optics and single photons. First we construct a heralded Fredkin gate using four heralded controlled-NOT (CNOT) gates. Then we simplify this method to a post-selected one utilizing only two CNOT gates. We also give a possible rea ... [Phys. Rev. A 78, 012305 (2008)] published Wed Jul 2, 2008.
We consider the realization of a quantum Fredkin gate with only linear optics and single photons. First we construct a heralded Fredkin gate using four heralded controlled-NOT (CNOT) gates. Then we simplify this method to a post-selected one utilizing only two CNOT gates. We also give a possible rea ... [Phys. Rev. A 78, 012305 (2008)] published Wed Jul 2, 2008.
Maximally entangling tripartite protocols for Josephson phase qubits
Andrei Galiautdinov and John M. Martinis
We introduce a suit of simple entangling protocols for generating tripartite Greenberger-Horne-Zeilinger and W states in systems with anisotropic exchange interaction g(XX+YY)+g-tilde ZZ. An interesting example is provided by macroscopic entanglement in Josephson phase qubits with capacitive (g-tild ... [Phys. Rev. A 78, 010305 (2008)] published Wed Jul 9, 2008.
We introduce a suit of simple entangling protocols for generating tripartite Greenberger-Horne-Zeilinger and W states in systems with anisotropic exchange interaction g(XX+YY)+g-tilde ZZ. An interesting example is provided by macroscopic entanglement in Josephson phase qubits with capacitive (g-tild ... [Phys. Rev. A 78, 010305 (2008)] published Wed Jul 9, 2008.
Robust control of quantized motional states of a chain of trapped ions by collective adiabatic passage
I. E. Linington, P. A. Ivanov, N. V. Vitanov, and M. B. Plenio
A simple technique for robust generation of vibrational Fock states in a chain of trapped ions is proposed. The method is fast and easy to implement, since only a single chirped laser pulse, simultaneously addressing all of the ions, is required. Furthermore, because the approach uses collective adi ... [Phys. Rev. A 77, 063837 (2008)] published Thu Jun 26, 2008.
A simple technique for robust generation of vibrational Fock states in a chain of trapped ions is proposed. The method is fast and easy to implement, since only a single chirped laser pulse, simultaneously addressing all of the ions, is required. Furthermore, because the approach uses collective adi ... [Phys. Rev. A 77, 063837 (2008)] published Thu Jun 26, 2008.
Universal quantum computation with trapped ions in thermal motion by adiabatic passage
Xun-Li Feng, Chunfeng Wu, C. H. Lai, and C. H. Oh
We propose a universal quantum computation scheme for trapped ions in thermal motion via the technique of adiabatic passage, which incorporates the advantages of both the adiabatic passage and the model of trapped ions in thermal motion. Our scheme is immune from the decoherence due to spontaneous e ... [Phys. Rev. A 77, 062336 (2008)] published Thu Jun 26, 2008.
We propose a universal quantum computation scheme for trapped ions in thermal motion via the technique of adiabatic passage, which incorporates the advantages of both the adiabatic passage and the model of trapped ions in thermal motion. Our scheme is immune from the decoherence due to spontaneous e ... [Phys. Rev. A 77, 062336 (2008)] published Thu Jun 26, 2008.
Interaction- and measurement-free quantum Zeno gates for universal computation with single-atom and single-photon qubits
Y. P. Huang and M. G. Moore
By extending the concept of interaction-free imaging to the few-atom level, we show that asymptotically on-demand interaction- and measurement-free quantum logic gates can be realized for both single-atom and single-photon qubits. The interaction-free feature suppresses the possibility of qubit deco ... [Phys. Rev. A 77, 062332 (2008)] published Thu Jun 19, 2008.
By extending the concept of interaction-free imaging to the few-atom level, we show that asymptotically on-demand interaction- and measurement-free quantum logic gates can be realized for both single-atom and single-photon qubits. The interaction-free feature suppresses the possibility of qubit deco ... [Phys. Rev. A 77, 062332 (2008)] published Thu Jun 19, 2008.
Continuous-variable quantum swapping gate between light and atoms
T. Takano, M. Fuyama, R. Namiki, and Y. Takahashi
In the face of the recent development of the time-domain detection method for short pulses, typically less than 1 microsecond, we consider a feasible method for a continuous variable quantum swapping gate between light polarization and atomic spin ensemble by three successive Faraday rotation intera ... [Phys. Rev. A 78, 010307 (2008)] published Tue Jul 15, 2008.
In the face of the recent development of the time-domain detection method for short pulses, typically less than 1 microsecond, we consider a feasible method for a continuous variable quantum swapping gate between light polarization and atomic spin ensemble by three successive Faraday rotation intera ... [Phys. Rev. A 78, 010307 (2008)] published Tue Jul 15, 2008.
Universal control of nuclear spins via anisotropic hyperfine interactions
J. S. Hodges, J. C. Yang, C. Ramanathan, and D. G. Cory
We propose a method for completely controlling a nuclear spin subsystem using only microwave irradiation of resolved anisotropic hyperfine interactions with a single electron spin. This paradigm of control has important applications for spin based solid-state quantum information processing. In parti ... [Phys. Rev. A 78, 010303 (2008)] published Tue Jul 8, 2008.
We propose a method for completely controlling a nuclear spin subsystem using only microwave irradiation of resolved anisotropic hyperfine interactions with a single electron spin. This paradigm of control has important applications for spin based solid-state quantum information processing. In parti ... [Phys. Rev. A 78, 010303 (2008)] published Tue Jul 8, 2008.
Demonstration of pure geometric universal single-qubit operation on two-level atoms
Hiromitsu Imai and Atsuo Morinaga
With carefully prepared resonant laser-controlled pulses, the two quantum states of a cold ensemble of sodium atoms were manipulated by pure geometric rotations of the Bloch vector around axes 2 and 3 on the Bloch sphere. The fidelity for two geometric rotations was improved to be 90%. A universal s ... [Phys. Rev. A 78, 010302 (2008)] published Wed Jul 2, 2008.
With carefully prepared resonant laser-controlled pulses, the two quantum states of a cold ensemble of sodium atoms were manipulated by pure geometric rotations of the Bloch vector around axes 2 and 3 on the Bloch sphere. The fidelity for two geometric rotations was improved to be 90%. A universal s ... [Phys. Rev. A 78, 010302 (2008)] published Wed Jul 2, 2008.
Nonlinear dispersive regime of cavity QED: The dressed dephasing model
Maxime Boissonneault, J. M. Gambetta, and Alexandre Blais
Systems in the dispersive regime of cavity quantum electrodynamics (QED) are approaching the limits of validity of the dispersive approximation. We present a model which takes into account nonlinear corrections to the dressing of the atom by the field. We find that in the presence of pure dephasing, ... [Phys. Rev. A 77, 060305 (2008)] published Tue Jun 17, 2008.
Systems in the dispersive regime of cavity quantum electrodynamics (QED) are approaching the limits of validity of the dispersive approximation. We present a model which takes into account nonlinear corrections to the dressing of the atom by the field. We find that in the presence of pure dephasing, ... [Phys. Rev. A 77, 060305 (2008)] published Tue Jun 17, 2008.