V. I. Tsifrinovich

Quantum computer on a class of one-dimensional Ising systems

Abstract We discuss the problem of designing a quantum computer based on one-dimensional “alternating” Ising systems (linear chains with periodically recurring spin groups) in an external magnetic field which exceeds the interaction between spins. Loading and processing of information in the alternating Ising system may be accomplished by using a scheme suggested recently by Lloyd for heteropolymer systems. The detailed operation of a simple quantum logical device is described in the framework of a binary Ising system. Estimates of physical parameters are presented that show that the experimental realization of such quantum computer elements would be feasible as a research task. However, many difficulties remain to be addressed, before the approach discussed here would be applicable in real devices.

Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy

We propose a nuclear-spin quantum computer based on magnetic resonance force microscopy ~MRFM! .I t is shown that an MRFM single-electron spin measurement provides three essential requirements for quantum computation in solids: ~a! preparation of the ground state, ~b! one- and two-qubit quantum logic gates, and ~c! a measurement of the final state. The proposed quantum computer can operate at temperatures up to 1 K.

Superradiance Transition in Photosynthetic Light-Harvesting Complexes

We investigate the role of long-lasting quantum coherence in the efficiency of energy transport at room temperature in Fenna-Matthews-Olson photosynthetic complexes. The excitation energy transfer due to coupling of the light-harvesting complex to the reaction center (“sink”) is analyzed using an effective non-Hermitian Hamiltonian. We show that, as the coupling to the reaction center is varied, maximal efficiency in energy transport is achieved in the vicinity of the superradiance transition, characterized by a segregation of the imaginary parts of the eigenvalues of the effective non-Hermitian Hamiltonian. Our results demonstrate that the presence of the sink (which provides a quasi-continuum in the energy spectrum) is the dominant effect in the energy transfer which takes place even in the absence of a thermal bath. This approach allows one to study the effects of finite temperature and the effects of any coupling scheme to the reaction center. Moreover, taking into account a realistic electric dipole ...

Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon

We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations.

Solid-State Quantum Computer Based on Scanning Tunneling Microscopy

We propose a solid-state nuclear-spin quantum computer based on application of scanning tunneling microscopy (STM) and well-developed silicon technology. It requires the measurement of tunneling-current modulation caused by the Larmor precession of a single electron spin. Our envisioned STM quantum computer would operate at the high magnetic field (approximately 10 T) and at low temperature approximately 1 K.

Measurement of single electron and nuclear spin states based on optically detected magnetic resonance

A novel approach for measurement of single electron and nuclear spin states is suggested. Our approach is based on optically detected magnetic resonance in a nano-probe located at the apex of an AFM tip. The method provides single electron spin sensitivity with nano-scale spatial resolution.

Magnetic resonance force microscopy and a single-spin measurement

Spin Dynamics -- Quasiclassical Description Spin Dynamics -- Quantum Description Mechanical Vibrations of the Cantilever Single-Spin Detection in Magnetic Force Microscopy (MFM) Transient Process in MFM -- The Exact Solution of the Master Equation Periodic Spin Reversals in Magnetic Resonance Force Microscopy (MRFM) Driven by -Pulses Oscillating Adiabatic Spin Reversals Driven by the Frequency Modulated rf Field Oscillating Cantilever-Driven Adiabatic Reversals (OSCAR) Technique in MRFM CT-Spin Dynamics in the OSCAR Technique Magnetic Noise and Spin Relaxation in OSCAR MRFM MRFM Applications: Measurement of an Entangled Spin State and Quantum Computation MRFM Techniques and Spin Diffusion.

Spin relaxation caused by thermal excitations of high-frequency modes of cantilever vibrations

We consider the process of spin relaxation in the oscillating cantilever-driven adiabatic reversals technique in magnetic-resonance force microscopy. We simulated the spin relaxation caused by thermal excitations of the high-frequency cantilever modes in the region of the Rabi frequency of the spin subsystem. The minimum relaxation time obtained in our simulations is greater than but of the same order of magnitude as one measured in recent experiments. We demonstrated that using a cantilever with nonuniform cross-sectional area may significantly increase spin-relaxation time.

Modified approach to single-spin detection using magnetic resonance force microscopy

The magnetic moment of a single spin interacting with a cantilever in magnetic resonance force microscopy (MRFM) experiences quantum jumps in orientation rather than smooth oscillations. These jumps cannot be detected by a conventional MRFM based on observation of driven resonant oscillations of a cantilever. In this paper, we propose a method which should allow detection of the magnetic signal from a single spin using a modification of a conventional MRFM. We estimate the opportunity to detect the magnetic signal from a single proton. (c) 2000 The American Physical Society.

Delocalization border and onset of chaos in a model of quantum computation

We show that a magnetic field gradient can suppress the onset of quantum chaos in a nuclear spin chain quantum computer.