Coherent Manipulation of Electron Spins in the {Cu} Spin Triangle Complex Impregnated in Nanoporous Silicon
K.-Y. Choi, Z. Wang, H. Nojiri, J. van Tol, P. Kumar et al.
We report on coherent manipulation of electron spins in an antiferromagnetically coupled spin triangle {Cu-X} (X=As, Sb) impregnated in freestanding nanoporous silicon (NS) by using 240 GHz microwave pulses. Rabi oscillations are observed and the spin coherence time is found to be T=1066 ns at 1.5 ... [Phys. Rev. Lett. 108, 067206 ] published .
Exploiting boundary states of imperfect spin chains for high-fidelity state transfer
M. Bruderer, K. Franke, S. Ragg, W. Belzig, and D. Obreschkow
We study transfer of a quantum state through XX spin chains with static imperfections. We combine the two standard approaches for state transfer based on (i) modulated couplings between neighboring spins throughout the spin chain and (ii) weak coupling of the outermost spins to an unmodulated spin c ... [Phys. Rev. A 85, 022312 ] published .
Avoidance of Majorana Resonances in Periodic Topological Superconductor-Nanowire Structures
Jay D. Sau, Chien Hung Lin, Hoi-Yin Hui, and S. Das Sarma
Semiconducting nanowires in proximity to superconductors are promising experimental systems for Majorana fermions which may ultimately be used as building blocks for topological quantum computers. A serious challenge in the experimental realization of the Majorana fermion in these semiconductor-supe ... [Phys. Rev. Lett. 108, 067001 ] published .
Temperature-independent quantum logic for molecular spectroscopy
Jordi Mur-Petit, Juan Jose Garcia-Ripoll, Jesus Perez-Rios, Jose Campos-Martinez, Marta I. Hernandez et al.
We propose a fast and nondestructive spectroscopic method for single molecular ions that implements quantum logic schemes between an atomic ion and the molecular ion of interest. Our proposal relies on a hybrid coherent manipulation of the two-ion system, using optical or magnetic forces depending o ... [Phys. Rev. A 85, 022308 ] published .
High-fidelity quantum gates in the presence of dispersion
B. Khani, S. T. Merkel, F. Motzoi, Jay M. Gambetta, and F. K. Wilhelm
We numerically demonstrate the control of motional degrees of freedom of an ensemble of neutral atoms in an optical lattice with a shallow trapping potential. Taking into account the range of quasimomenta across different Brillouin zones results in an ensemble whose members effectively have inhomoge ... [Phys. Rev. A 85, 022306 ] published .
Back-action of a driven nonlinear resonator on a superconducting qubit
Maxime Boissonneault, A. C. Doherty, F. R. Ong, P. Bertet, D. Vion et al.
We study the backaction of a driven nonlinear resonator on a multilevel superconducting qubit. Using unitary transformations on the multilevel Jaynes-Cummings Hamiltonian and quantum optics master equation, we derive an analytical model that goes beyond linear response theory. Within the limits of v ... [Phys. Rev. A 85, 022305 ] published .
Nonlocality as a benchmark for universal quantum computation in Ising anyon topological quantum computers
Mark Howard and Jiri Vala
An obstacle affecting any proposal for a topological quantum computer based on Ising anyons is that quasiparticle braiding can only implement a finite (nonuniversal) set of quantum operations. The computational power of this restricted set of operations (often called stabilizer operations) has been ... [Phys. Rev. A 85, 022304 ] published .
Control of inhomogeneous atomic ensembles of hyperfine qudits
Brian E. Mischuck, Seth T. Merkel, and Ivan H. Deutsch
We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the des ... [Phys. Rev. A 85, 022302 ] published .
Characterization of a Two-Transmon Processor with Individual Single-Shot Qubit Readout
A. Dewes, F. R. Ong, V. Schmitt, R. Lauro, N. Boulant et al.
We report the characterization of a two-qubit processor implemented with two capacitively coupled tunable superconducting qubits of the transmon type, each qubit having its own nondestructive single-shot readout. The fixed capacitive coupling yields the sqrt(iSWAP) two-qubit gate for a suitable inte ... [Phys. Rev. Lett. 108, 057002 ] published .
Fast Path and Polarization Manipulation of Telecom Wavelength Single Photons in Lithium Niobate Waveguide Devices
Damien Bonneau, Mirko Lobino, Pisu Jiang, Chandra M. Natarajan, Michael G. Tanner et al.
We demonstrate fast polarization and path control of photons at 1550 nm in lithium niobate waveguide devices using the electro-optic effect. We show heralded single photon state engineering, quantum interference, fast state preparation of two entangled photons, and feedback control of quantum interf ... [Phys. Rev. Lett. 108, 053601 ] published .
Parallel density matrix propagation in spin dynamics simulations
Luke J. Edwards and Ilya Kuprov
Several methods for density matrix propagation in parallel computing environments are proposed and evaluated. It is demonstrated that the large communication overhead associated with each propagation step (two-sided multiplication of the density matrix by an exponential propagator and its conjugate) ... [J. Chem. Phys. 136, 044108 (2012)] published Tue Jan 31, 2012.
Accelerating Quantum Monte Carlo Simulations of Real Materials on GPU Clusters
Kenneth P. Esler, Jeongnim Kim, David M. Ceperley, and Luke Shulenburger
More accurate than mean-field methods and more scalable than quantum chemical methods, continuum quantum Monte Carlo (QMC) is an invaluable tool for predicting the properties of matter from fundamental principles. Because QMC algorithms offer multiple forms of parallelism, they're ideal candidates f ... [Comput. Sci. Eng. 14, 40 (2012)] published Tue Jan 31, 2012.
Fast generation of multiparticle entangled state for flux qubits in a circle array of transmission line resonators with tunable coupling
Z. H. Peng, Yu-xi Liu, Y. Nakamura, and J. S. Tsai
We study a one-step approach to the fast generation of Greenberger-Horne-Zeilinger (GHZ) states in a circuit QED system with superconducting flux qubits. The GHZ state can be generated in about 10 ns, which is much shorter than the coherence time of flux qubits and comparable with the time of single ... [Phys. Rev. B 85, 024537 ] published .
Storage and retrieval of a microwave field in a spin ensemble
Y. Kubo, I. Diniz, A. Dewes, V. Jacques, A. Dreau et al.
We report the storage and retrieval of a small microwave field from a superconducting resonator into collective excitations of a spin ensemble. The spins are nitrogen-vacancy centers in a diamond crystal. The storage time of the order of 30 ns is limited by inhomogeneous broadening of the spin ensem ... [Phys. Rev. A 85, 012333 ] published .
Trapping a particle of a quantum walk on the line
Antoni Wojcik, Tomasz Luczak, Pawel Kurzynski, Andrzej Grudka, Tomasz Gdala et al.
We observe that changing a phase at a single point in a discrete quantum walk results in a rather surprising localization effect. For certain values of this phase change the possibility of localization strongly depends on the internal coin state of the walker. ... [Phys. Rev. A 85, 012329 ] published .
Schmidt-number benchmark for genuine quantum memories and gates
Ryo Namiki and Yuuki Tokunaga
We propose to apply the notion of the Schmidt number in order to show that a quantum memory or gate process is capable of maintaining a genuine multilevel quantum coherence. We present a simple criterion in terms of an average gate fidelity with respect to the input states of two mutually unbiased b ... [Phys. Rev. A 85, 010305 ] published .
Dipole Coupling of a Double Quantum Dot to a Microwave Resonator
T. Frey, P. J. Leek, M. Beck, A. Blais, T. Ihn et al.
We demonstrate the realization of a hybrid solid-state quantum device, in which a semiconductor double quantum dot is dipole coupled to the microwave field of a superconducting coplanar waveguide resonator. The double dot charge stability diagram extracted from measurements of the amplitude and phas ... [Phys. Rev. Lett. 108, 046807 ] published .
Configuration interaction calculations of the controlled phase gate in double quantum dot qubits
Erik Nielsen, Richard P. Muller, and Malcolm S. Carroll
We consider qubit coupling resulting from the capacitive coupling between two double quantum dot (DQD) singlet-triplet qubits. Calculations of the coupling when the two DQDs are detuned symmetrically or asymmetrically are performed using a full configuration interaction (CI). The full CI reveals beh ... [Phys. Rev. B 85, 035319 ] published .
Quantum state transfer between hybrid qubits in a circuit QED
Zhi-Bo Feng
In this Brief Report, we propose a theoretical scheme to transfer quantum states between superconducting charge qubits and semiconductor spin qubits in a circuit QED device. Under dispersive conditions, resonator-assisted state transfer between qubits can be performed controllably only by addressing ... [Phys. Rev. A 85, 014302 ] published .
Cluster-state generation using van der Waals and dipole-dipole interactions in optical lattices
Elena Kuznetsova, T. Bragdon, Robin Cote, and S. F. Yelin
We present a scalable method for generation of a cluster state for measurement-based quantum computing using van der Waals or dipole-dipole interactions between neutral atoms or polar molecules in an optical lattice. Nearest neighbor entanglement is accomplished by performing a phase gate using inte ... [Phys. Rev. A 85, 012328 ] published .
Benchmarking a Quantum Teleportation Protocol in Superconducting Circuits Using Tomography and an Entanglement Witness
M. Baur, A. Fedorov, L. Steffen, S. Filipp, M. P. da Silva et al.
Teleportation of a quantum state may be used for distributing entanglement between distant qubits in quantum communication and for quantum computation. Here we demonstrate the implementation of a teleportation protocol, up to the single-shot measurement step, with superconducting qubits coupled to a ... [Phys. Rev. Lett. 108, 040502 ] published .