arXiv subjects

Alexander R. Kessel

Publications and source records attributed to Alexander R. Kessel.

7 recordsLinked to original sources

arXiv2002

Schemes of implementation in NMR of quantum processors and Deutsch-Jozsa algorithm by using virtual spin representation

Schemes of experimental realization of the main two qubit processors for quantum computers and Deutsch-Jozsa algorithm are derived in virtual spin representation. The results are applicable for every four quantum states allowing the required properties for quantum processor implementation if for qubit encoding virtual spin representation is used. Four dimensional Hilbert space of nuclear spin 3/2 is considered in details for this aim

quant-ph↗

arXiv2000

Quantum entanglement and classical separability in NMR computing

In the discussion about the quantumness of NMR computation a conclusion is done that computational states are separable and therefore can not be entangled. This conclusion is based on the assumption that the initial density matrix of an individual molecule coincides with whole sample molecules distribution over single molecule energy levels. This means that quantum stochasticity is replaced by classical stochasticity. In the present paper it is shown, that quantum NMR computation can create genuine entangled states if initial system states are thermodynamical equilibrium ones. A separability analysis problem can arise when one interprets the readout signal from whole sample.

quant-ph↗

arXiv2000

Delocalized Qubits as a Computational Basis in the System of Interacting Spins

It is suggested to map the qubits into solid state NMR spin system collective states instead of the states of the individual spin. Such an approach introduces the stable computational basis without any additional actions and allows to obtain the universal set of quantum gates, which operation time is determined only by a RF pulse duration.

quant-ph↗

arXiv2000

Three-Qubit Gate Realization Using Single Quantum Particle

Using virtual spin formalism it is shown that a quantum particle with eight energy levels can store three qubits. The formalism allows to realize a universal set of quantum gates. Feasible formalism implementation is suggested which uses nuclear spin-7/2 as a storage medium and radio frequency pulses as the gates. One pulse realization of all universal gates has been found, including three-qubit Toffoli gate.

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arXiv2000

Four Atomic Optical Energy Levels as a Two Qubit Quantum Computer Register

It is proposed to use four atomic optical energy levels as a two qubit quantum register. A single Pr3+ atom in a monocrystal LaF3 subjected to resonant laser irradiation is used as an example to illustrate the implementation of the universal set of quantum gates. The equilibrium state of this physical system is a desirable input state for quantum computation and therefore there is no need for its special preparation procedure.

quant-ph↗

arXiv1999

Multilevel Quantum Particle as a Few Virtual Qubits Materialization

A conception of virtual quantum information bit - virtual qubit - is introduced. It is shown by means of virtual qubit representation that four states of a single quantum particle is enough for implementation of full set of the gates, which is necessary for creation an arbitrary algorithm for a quantum computer. The physical nature and mutual disposition of four working states is of no significance, if there are suitable selection rules for the particle interaction with the external electromagnetic field pulses.

quant-ph↗

arXiv1999

Multiqubit Spin

It is proposed that the state space of a quantum object with a complicated discrete spectrum can be used as a basis for multiqubit recording and processing of information in a quantum computer. As an example, nuclear spin 3/2 is considered. The possibilities of writing and reading two quantum bits of information, preparation of the initial state, implementation of the "rotation" and "controlled negation" operations, which are sufficient for constructing any algorithms, are demonstrated.

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