Publications (28)
Fast Amplification and Rephasing of Entangled Cat States in a Qubit-Oscillator System
Z. Xiao, T. Fuse, S. Ashhab +5
We study a qubit-oscillator system, with a time-dependent coupling coefficient, and present a scheme for generating entangled Schrödinger-cat states with large mean photon numbers…
Spectroscopy of SrRuO/Ru Junctions in Eutectic
H. Yaguchi, K. Takizawa, M. Kawamura +6
We have investigated the tunnelling properties of the interface between superconducting Sr2RuO4 and a single Ru inclusion in eutectic. By using a micro-fabrication technique, we ha…
Coupling superconducting flux qubits at optimal point via dynamic decoupling with the quantum bus
Y. D. Wang, A. Kemp, K. Semba
We propose a scheme with dc-control of finite bandwidth to implement two-qubit gate for superconducting flux qubits at the optimal point. We provide a detailed non-perturbative ana…
Cooling of a Micro-mechanical Resonator by the Back-action of Lorentz Force
Y. D. Wang, K. Semba, H. Yamaguchi
Using a semi-classical approach, we describe an on-chip cooling protocol for a micro-mechanical resonator by employing a superconducting flux qubit. A Lorentz force, generated by t…
Vacuum Rabi oscillations in a macroscopic superconducting qubit LC oscillator system
J. Johansson, S. Saito, T. Meno +4
We have observed the coherent exchange of a single energy quantum between a flux qubit and a superconducting LC circuit acting as a quantum harmonic oscillator. The exchange of an…
Fabrication and properties of MgB2/AlOx/MgB2 tunnel junctions
K. Ueda, S. Saito, K. Semba +2
Sandwich-type MgB2 Josephson tunnel junctions (MgB2/AlOx/MgB2) have been fabricated using as-grown MgB2 films formed by molecular beam epitaxy. The junctions exhibited substantial…
Analysis of the spectroscopy of a hybrid system composed of a superconducting flux qubit and diamond NV centers
H. Cai, Y. Matsuzaki, K. Kakuyanagi +8
A hybrid system that combines the advantages of a superconducting flux qubit and an electron spin ensemble in diamond is one of the promising devices to realize quantum information…
Multiphoton transitions in a macroscopic quantum two-state system
S. Saito, M. Thorwart, H. Tanaka +4
We have observed multiphoton transitions between two macroscopic quantum-mechanical superposition states formed by two opposite circulating currents in a superconducting loop with…
Cooling a micro-mechanical resonator by quantum back-action from a noisy qubit
Ying-Dan Wang, Yong Li, Fei Xue +2
We study the role of qubit dephasing in cooling a mechanical resonator by quantum back-action. With a superconducting flux qubit as a specific example, we show that ground-state co…
On-chip quantum feedback control of a superconducting qubit
K. Kakuyanagi, A. Kemp, T. Baba +4
Quantum feedback is a technique for measuring a qubit and applying appropriate feedback depending on the measurement results. Here, we propose a new on-chip quantum feedback method…
Controllable Coupling between Flux Qubit and Nanomechanical Resonator by Magnetic Field
Fei Xue, Y. D Wang, C. P. Sun +3
We propose an active mechanism for coupling the quantized mode of a nanomechanical resonator to the persistent current in the loop of a superconducting Josephson junction (or phase…
Phase-Coherent Dynamics of a Superconducting Flux Qubit with Capacitive-Bias Readout
F. Deppe, M. Mariantoni, E. P. Menzel +7
We present a systematic study of the phase-coherent dynamics of a superconducting three-Josephson-junction flux qubit. The qubit state is detected with the integrated-pulse method,…
Relaxation and Dephasing in a Flux-qubit
P. Bertet, I. Chiorescu, G. Burkard +4
We report detailed measurements of the relaxation and dephasing time in a flux-qubit measured by a switching DC SQUID. We studied their dependence on the two important circuit bias…
Superradiance phase transition in the presence of parameter fluctuations
S. Ashhab, K. Semba
We theoretically analyze the effect of parameter fluctuations on the superradiance phase transition in a setup where a large number of superconducting qubits are coupled to a singl…
Coherent dynamics of a flux qubit coupled to a harmonic oscillator
I. Chiorescu, P. Bertet, K. Semba +3
In the emerging field of quantum computation and quantum information, superconducting devices are promising candidates for the implementation of solid-state quantum bits or qubits.…
Persistent Supercurrent Atom Chip
T. Mukai, C. Hufnagel, A. Kasper +4
Rubidium 87 atoms are trapped in an Ioffe-Pritchard potential generated with a persistent supercurrent that flows in a loop circuit patterned on a sapphire surface. The superconduc…
Electrical Detection and Magnetic-Field Control of Spin States in Phosphorus-Doped Silicon
H. Morishita, L. S. Vlasenko, H. Tanaka +5
Electron paramagnetic resonance of ensembles of phosphorus donors in silicon has been detected electrically with externally applied magnetic fields lower than 200 G. Because the sp…
Readout strength dependence of state projection in superconducting qubit
K. Kakuyanagi, H. Nakano, S. Kagei +4
We have controlled the measurement strength of the qubit readout process by using a Josephson bifurcation amplifier (JBA : an AC-driven SQUID). The optimum readout pulse changes th…
All-MgB2 Josephson tunnel junctions
K. Ueda, S. Saito, K. Semba +2
Sandwich-type all-MgB2 Josephson tunnel junctions (MgB2/AlOx/MgB2) have been fabricated for the first time with as-grown MgB2 films formed by molecular beam epitaxy. The junctions…
Dephasing of a superconducting qubit induced by photon noise
P. Bertet, I. Chiorescu, G. Burkard +4
We have studied the dephasing of a superconducting flux-qubit coupled to a DC-SQUID based oscillator. By varying the bias conditions of both circuits we were able to tune their eff…
Long-range and selective coupler for superconducting flux qubits
H. Nakano, K. Kakuyanagi, M. Ueda +1
We propose a qubit-qubit coupling scheme for superconducting flux quantum bits (qubits), where a quantized Josephson junction resonator and microwave irradiation are utilized. The…
Two-photon probe of the Jaynes-Cummings model and symmetry breaking in circuit QED
Frank Deppe, Matteo Mariantoni, E. P. Menzel +9
Superconducting qubits behave as artificial two-level atoms and are used to investigate fundamental quantum phenomena. In this context, the study of multi-photon excitations occupi…
Spectrum of the Dicke model in a superconducting qubit-oscillator system
S. Ashhab, Y. Matsuzaki, K. Kakuyanagi +4
We calculate the transmission spectrum of a superconducting circuit realization of the Dicke model and identify spectroscopic features that can serve as signatures of the superradi…
A theoretical analysis of flux-qubit measurements with a dc-SQUID
H. Nakano, H. Tanaka, S. Saito +3
The readout process of a superconducting flux-qubit is theoretically analyzed in terms of the quantum dynamics of a qubit-SQUID coupled system during measurement. The quantity dire…
Parametric control of a superconducting flux qubit
S. Saito, T. Meno, M. Ueda +3
Parametric control of a superconducting flux qubit has been achieved by using two-frequency microwave pulses. We have observed Rabi oscillations stemming from parametric transition…
Experimentally Realizable C-NOT Gate in a Flux Qubit/Resonator System
S. Saito, T. Tilma, S. J. Devitt +2
In this paper we present an experimentally realizable microwave pulse sequence that effects a Controlled NOT (C-NOT) gate operation on a Josephson junction-based flux-qubit/resonat…
Detection of a persistent-current qubit by resonant activation
P. Bertet, I. Chiorescu, K. Semba +2
We present the implementation of a new scheme to detect the quantum state of a persistent-current qubit. It relies on the dependency of the measuring Superconducting Quantum Interf…
Dephasing of a superconducting flux qubit
K. Kakuyanagi, T. Meno, S. Saito +5
In order to gain a better understanding of the origin of decoherence in superconducting flux qubits, we have measured the magnetic field dependence of the characteristic energy rel…