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Quantum Thermodynamic Cycles and quantum heat engines
H. T. Quan, Yu-xi Liu, C. P. Sun +1
In order to describe quantum heat engines, here we systematically study isothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum vers…
Enhancement of entanglement transfer in a spin chain by phase shift-control
K. Maruyama, T. Iitaka, F. Nori
We study the effect of a phase shift on the amount of transferrable two-spin entanglement in a spin chain. We consider a ferromagnetic Heisenberg/XY spin chain, both numerically an…
Observing quantum non-locality in the entanglement between modes of massive particles
S. Ashhab, Koji Maruyama, Franco Nori
We consider the question of whether it is possible to use the entanglement between spatially separated modes of massive particles to observe nonlocal quantum correlations. Mode ent…
Efficient one-step generation of large cluster states with solid-state circuits
J. Q. You, Xiang-bin Wang, Tetsufumi Tanamoto +1
Highly entangled states called cluster states are a universal resource for measurement-based quantum computing (QC). Here we propose an efficient method for producing large cluster…
Low-decoherence flux qubit
J. Q. You, Xuedong Hu, S. Ashhab +1
A flux qubit can have a relatively long decoherence time at the degeneracy point, but away from this point the decoherence time is greatly reduced by dephasing. This limits the pra…
Measurement-based quantum computation with superconducting charge qubits
Xiang-bin Wang, J. Q. You, Franco Nori
We present a robust method, based only on measurements, to produce superconducting cluster states. The measurement of the current of a few parallel Josephson-junction qubits realiz…
Decoherence in a scalable adiabatic quantum computer
S. Ashhab, J. R. Johansson, Franco Nori
We consider the effects of decoherence on Landau-Zener crossings encountered in a large-scale adiabatic-quantum-computing setup. We analyze the dependence of the success probabilit…
Quantum Tera-Hertz electrodynamics in Layered Superconductors
Sergey Savel'ev, A. L. Rakhmanov, Franco Nori
In close analogy to quantum electrodynamics, we derive a quantum field theory of Josephson plasma waves (JPWs) in layered superconductors (LSCs), which describes two types of inter…
Scalable superconducting qubit circuits using dressed states
Yu-xi Liu, C. P. Sun, Franco Nori
We study a coupling/decoupling method between a superconducting qubit and a data bus that uses a controllable time-dependent electromagnetic field (TDEF). As in recent experiments,…
Nonuniform Self-Organized Dynamical States in Superconductors with Periodic Pinning
V. R. Misko, S. Savel'ev, A. L. Rakhmanov +1
We consider magnetic flux moving in superconductors with periodic pinning arrays. We show that sample heating by moving vortices produces negative differential resistivity (NDR) of…
Sculpting microscopic magnetic flux landscapes in a BSCCO2212 vortex lens
D. Cole, S. J. Bending, S. Savelev +2
We demonstrate experimentally that the micromagnetic profile of the out-of-plane component of magnetic induction, B_z, in the crossing lattices regime of layered superconductors ca…
Generalized switchable coupling for superconducting qubits using double resonance
S. Ashhab, Shigemasa Matsuo, Noriyuki Hatakenaka +1
We propose a method for switchable coupling between superconducting qubits using double resonance. The inter-qubit coupling is achieved by applying near-resonant oscillating fields…
Switchable resonant coupling of flux qubits
M. Grajcar, Yu-xi Liu, Franco Nori +1
We propose a coupling scheme, where two or more flux qubits with different eigenfrequencies share Josephson junctions with a coupler loop devoid of its own quantum dynamics. Switch…
Decoherence and Rabi oscillations in a qubit coupled to a quantum two-level system
S. Ashhab, J. R. Johansson, Franco Nori
In this paper we review some of our recent results on the problem of a qubit coupled to a quantum two-level system. We consider both the decoherence dynamics and the qubit's respon…
Fluctuation-Induced Casimir Forces in Granular Fluids
C. Cattuto, R. Brito, U. Marini Bettolo Marconi +2
We have numerically investigated the behavior of driven non-cohesive granular media and found that two fixed large intruder particles, immersed in a sea of small particles, experie…
Quantum two-level systems in Josephson junctions as naturally formed qubits
A. M. Zagoskin, S. Ashhab, J. R. Johansson +1
The two-level systems (TLSs) naturally occurring in Josephson junctions constitute a major obstacle for the operation of superconducting phase qubits. Since these TLSs can possess…
Producing cluster states in charge qubits and flux qubits
Tetsufumi Tanamoto, Yu-xi Liu, Shinobu Fujita +2
We propose a method to efficiently generate cluster states in charge qubits, both semiconducting and superconducting, as well as flux qubits. We show that highly-entangled cluster…
Rabi oscillations in a qubit coupled to a quantum two-level system
S. Ashhab, J. R. Johansson, Franco Nori
We consider the problem of a qubit driven by a harmonically oscillating external field while it is coupled to a quantum two-level system. We perform a systematic numerical analysis…
Superconducting Circuits and Quantum Information
J. Q. You, Franco Nori
Superconducting circuits can behave like atoms making transitions between two levels. Such circuits can test quantum mechanics at macroscopic scales and be used to conduct atomic-p…
Macroscopic Quantum Criticality in a Circuit QED
Y. D. Wang, H. T. Quan, Yu-xi Liu +2
Cavity quantum electrodynamic (QED) is studied for two strongly-coupled charge qubits interacting with a single-mode quantized field, which is provided by a on-chip transmission li…
Quantum electromechanics: Quantum tunneling near resonance and qubits from buckling nanobars
Sergey Savel'ev, Xuedong Hu, A. Kasumov +1
Analyzing recent experimental results, we find similar behaviors and a deep analogy between three-junction superconducting qubits and suspended carbon nanotubes. When these differe…
Probing tiny motions of nanomechanical resonators: classical or quantum mechanical?
L. F. Wei, Yu-xi Liu, C. P. Sun +1
We propose a spectroscopic approach to probe tiny vibrations of a nanomechanical resonator (NAMR), which may reveal classical or quantum behavior depending on the decoherence-induc…