109 research outputs found
Anderson-type model for a molecule adsorbed on a metal surface
We investigate a modified Anderson model to study the local density of states
(LDOS) of a molecular wire adsorbed on a metal. Using a self-consistent
mean-field type approach we find an exponential decay of the LDOS along the
molecule. A repulsive on-site interaction on the molecule suppresses the
tunneling and decreases the characteristic decay length.Comment: 7 pages (using europhys.sty), 5 EPS figures, To appear in Europhys.
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Coupling Circuit Resonators Among Themselves and To Nitrogen-Vacancy Centers in Diamond
We propose a scheme to couple NV centers in diamond through coplanar
waveguide resonators. The central conductor of the resonator is split into
several pieces which are coupled strongly with each other via simple capacitive
junctions or superconducting Josephson junctions. The NV centers are then put
at the junctions. The discontinuity at the junctions induces a large local
magnetic field, with which the NV centers are strongly coupled to the circuit
resonator. The coupling strength between the resonator and the NV center is
of order of --30\unit{MHz}.Comment: 4 pages; 3 figures; several typos corrected; figure 1 regenerate
Single-Qubit Reaped Quantum State Tomography
Quantum state tomography is the experimental procedure of determining an
unknown state. It is not only essential for the verification of resources and
processors of quantum information but is also important in its own right with
regard to the foundation of quantum mechanics. Standard methods have been
elusive for large systems because of the enormous number of observables to be
measured and the exponential complexity of data post-processing. Here, we
propose a new scheme of quantum state tomography that requires the measurement
of only three observables (acting jointly on the system and pointer) regardless
of the size of the system. The system is coupled to a "pointer" of single
qubit, and the wavefunction of the system is "reaped" onto the pointer upon the
measurement of the system. Subsequently, standard two-state tomography on the
pointer and classical post-processing are used to reconstruct the quantum state
of the system. We also developed an efficient and scalable iterative maximum
likelihood algorithm to estimate states from statistically incomplete data.Comment: three figure
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