Non-local universal gates generated within a resonant magnetic cavity

Quantum Information is a quantum resource being advised as a useful tool to set up information processing. Despite physical components being considered are normally two-level systems, still the combination of some of them together with their entangling interactions (another key property in the quantum information processing) become in a complex dynamics needing be addressed and modeled under precise control to set programmed quantum processing tasks. Universal quantum gates are simple controlled evolutions resembling some classical computation gates. Despite their simple forms, not always become easy fit the quantum evolution to them. SU(2) decomposition is a mechanism to reduce the dynamics on SU(2) operations in composed quantum processing systems. It lets an easier control of evolution into the structure required by those gates by the adequate election of the basis for the computation grammar. In this arena, SU(2) decomposition has been studied under piecewise magnetic field pulses. Despite, it is completely applicable for time-dependent pulses, which are more affordable technologically, could be continuous and then possibly free of resonant effects. In this work, we combine the SU(2) reduction with linear and quadratic numerical approaches in the solving of time-dependent Schr\"odinger equation to model and to solve the controlled dynamics for two-qubits, the basic block for composite quantum systems being analyzed under the SU(2) reduction. A comparative benchmark of both approaches is presented together with some useful outcomes for the dynamics in the context of quantum information processing operations.

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SCHEME FOR QUANTUM CLONING AND QUANTUM INFORMATION PROCESSING WITH TRAPPED IONS

Modern Physics Letters B ◽

10.1142/s0217984907013158 ◽

2007 ◽

Vol 21 (12) ◽

pp. 729-735

Author(s):

ZHI-MING ZHAN

Keyword(s):

Information Processing ◽

Quantum Information ◽

Quantum Information Processing ◽

Vibrational Mode ◽

Trapped Ions ◽

Distinct Advantage ◽

Quantum Cloning ◽

Universal Quantum ◽

Data Bus

In this paper, a scheme is presented to implement the 1→2 universal quantum cloning machine (UQCM) with trapped ions. In this way, we also show that quantum information can be directly transferred from one ion to another. The distinct advantage of the scheme lies in the fact that it does not use the vibrational mode as the data bus. The vibrational mode is only virtually excited, which makes our scheme insensitive to heating, provided the system remains in the Lamb–Dicke regime.

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Quantum information processing

Quantum Information ◽

10.1093/oso/9780198527626.003.0009 ◽

2009 ◽

Author(s):

Stephen Barnett

Keyword(s):

Information Processing ◽

Quantum Information ◽

Unitary Transformation ◽

Quantum Information Processing ◽

Quantum Computer ◽

Quantum Evolution ◽

Quantum Computers ◽

Digital Electronics ◽

Logic Operations ◽

And Control

We have seen how information can be encoded onto a quantum system by selecting the state in which it is prepared. Retrieving the information is achieved by performing a measurement, and the optimal measurement in any given situation is usually a generalized measurement. In between preparation and measurement, the information resides in the quantum state of the system, which evolves in a manner determined by the Hamiltonian. The associated unitary transformation may usefully be viewed as quantum information processing; if we can engineer an appropriate Hamiltonian then we can use the quantum evolution to assist in performing computational tasks. Our objective in quantum information processing is to implement a desired unitary transformation. Typically this will mean coupling together a number, perhaps a large number, of qubits and thereby generating highly entangled states. It is fortunate, although by no means obvious, that we can realize any desired multiqubit unitary transformation as a product of a small selection of simple transformations and, moreover, that each of these need only act on a single qubit or on a pair of qubits. The situation is reminiscent of digital electronics, in which logic operations are decomposed into actions on a small number of bits. If we can realize and control a very large number of such operations in a single device then we have a computer. Similar control of a large number of qubits will constitute a quantum computer. It is the revolutionary potential of quantum computers, more than any other single factor, that has fuelled the recent explosion of interest in our subject. We shall examine the remarkable properties of quantum computers in the next chapter. In digital electronics, we represent bit values by voltages: the logical value 1 is a high voltage (typically +5 V) and 0 is the ground voltage (0 V). The voltage bits are coupled and manipulated by transistor-based devices, or gates. The simplest gates act on only one bit or combine two bits to generate a single new bit, the value of which is determined by the two input bits. For a single bit, with value 0 or 1, the only possible operations are the identity (which does not require a gate) and the bit flip.

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