Stefano Chesi
University of Basel
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Publication
Featured researches published by Stefano Chesi.
New Journal of Physics | 2010
Stefano Chesi; Daniel Loss; Sergey Bravyi; Barbara M. Terhal
We discuss several thermodynamic criteria that have been introduced to characterize the thermal stability of a self-correcting quantum memory. We first examine the use of symmetry-breaking fields in analyzing the properties of self-correcting quantum memories in the thermodynamic limit; we show that the thermal expectation values of all logical operators vanish for any stabilizer and any subsystem code in any spatial dimension. On the positive side, we generalize the results of Alicki et al to obtain a general upper bound on the relaxation rate of a quantum memory at nonzero temperature, assuming that the quantum memory interacts via a Markovian master equation with a thermal bath. This upper bound is applicable to quantum memories based on either stabilizer or subsystem codes.
Physical Review A | 2015
Ying-Dan Wang; Stefano Chesi; Aashish A. Clerk
We provide analytic insight into the generation of stationary itinerant photon entanglement in a 3-mode optomechanical system. We identify the parameter regime of maximal entanglement, and show that strong entanglement is possible even for weak many-photon optomechanical couplings. We also show that strong tripartite entanglement is generated between the photonic and phononic output fields; unlike the bipartite photon-photon entanglement, this tripartite entanglement diverges as one approaches the boundary of system stability.
Physical Review B | 2010
Ying-Dan Wang; Stefano Chesi; Daniel Loss; Christoph Bruder
We propose a one-step scheme to generate Greenberger-Horne-Zeilinger (GHZ) states for superconducting flux qubits or charge qubits in a circuit QED setup. The GHZ state can be produced within the coherence time of the multiqubit system. Our scheme is independent of the initial state of the transmission line resonator and works in the presence of higher harmonic modes. Our analysis also shows that the scheme is robust to various operation errors and environmental noise.
Physical Review Letters | 2011
Stefano Chesi; Gabriele F. Giuliani; Leonid P. Rokhinson; L. N. Pfeiffer; K. W. West
Evidence is presented for the finite wave vector crossing of the two lowest one-dimensional spin-split subbands in quantum point contacts fabricated from two-dimensional hole gases with strong spin-orbit interaction. This phenomenon offers an elegant explanation for the anomalous sign of the spin polarization filtered by a point contact, as observed in magnetic focusing experiments. Anticrossing is introduced by a magnetic field parallel to the channel or an asymmetric potential transverse to it. Controlling the magnitude of the spin splitting affords a novel mechanism for inverting the sign of the spin polarization.
Physical Review B | 2010
Stefano Chesi; Daniel Loss
We study theoretically the statistical properties of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between localized magnetic moments in a disordered two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit couplings. Averaging over disorder, the static spin susceptibility tensor is evaluated diagrammatically in the mesoscopic (phase-coherent) regime. The disorder-averaged susceptibility leads to a twisted exchange interaction suppressed exponentially with distance, whereas the second-order correlations, which determine the fluctuations (variance) of the RKKY energy, decay with the same power-law as in the clean case. We obtain analytic expressions in the limits of large/small spin orbit interactions and for equal Rashba and Dresselhaus couplings. Beside these limiting cases, we study numerically the variance of the RKKY interaction in the presence of pure Rashba spin-orbit coupling. Our results are relevant for magnetic impurities or nuclear moments embedded in III-V two-dimensional heterostructures or in contact with surface states of metals and metal alloys, which can display a sizable Rashba spin-orbit coupling.
Physical Review Letters | 2008
Stefano Chesi; Daniel Loss
The competition between the Zeeman energy and the Rashba and Dresselhaus spin-orbit couplings is studied for fractional quantum Hall states by including correlation effects. A transition of the direction of the spin polarization is predicted at specific values of the Zeeman energy. We show that these values can be expressed in terms of the pair-correlation function, and thus provide information about the microscopic ground state. We examine the particular examples of the Laughlin wave functions and the 5/2-Pfaffian state. We also include effects of the nuclear bath.
Physical Review X | 2017
Hui Shao; Yan Qi Qin; Sylvain Capponi; Stefano Chesi; Zi Yang Meng; Anders W. Sandvik
We study the dynamic spin structure factor of the spin-
Bulletin of the American Physical Society | 2011
Fabio L. Pedrocchi; Stefano Chesi; Daniel Loss
1/2
Physical Review B | 2007
Stefano Chesi; Gabriele F. Giuliani
square-lattice Heisenberg antiferromagnet and of the
Physical Review B | 2007
Stefano Chesi; Gabriele F. Giuliani
J