Quantum Swap Research Articles

Realization of quantum SWAP gate between flying and stationary qubits

This paper presents a scheme to realize the SWAP gate between flying and stationary qubits through cavity QED, which is a necessary condition for networkability of quantum computation. As application, the storage of quantum information and teleportation of atomic and ionic states are present.

An energy relaxation tolerant approach to quantum entanglement, information transfer,and gates with superconducting-quantum-interference-device qubits in cavityQED

A scheme is proposed for realizing quantum entanglement, information transfer,CNOT gates, and SWAP gates with superconducting-quantum-interference-device(SQUID) qubits in cavity QED. In the scheme, the two logical states of a qubitare the two lowest levels of the SQUID. An intermediate level of the SQUIDis utilized to facilitate coherent control and manipulation of quantum states ofthe qubits. The method presented here does not involve a real excitation of theintermediate levels during the operations. Thus, decoherence due to energy relaxation ofintermediate levels is minimized. In addition, the present method does not require theadjustment of the SQUID level spacings, which simplifies the operation significantly.

Dynamics of a single trapped ion inside a nonideal QED cavity at zero temperature

We consider a system consisting of a single ion in a Paul trap coupled to a cavity electromagnetic field mode. We analyze the fidelity of a scheme for quantum swapping between vibrational and cavity field states, when the system is in contact with a reservoir at zero temperature.

Toward a scalable, silicon-based quantum computing architecture

Advances in quantum devices have brought scalable quantum computation closer to reality. We focus on the system-level issues of how quantum devices can be brought together to form a scalable architecture. In particular, we examine promising silicon-based proposals. We discover that communication of quantum data is a critical resource in such proposals. We find that traditional techniques using quantum SWAP gates are exponentially expensive as distances increase and propose quantum teleportation as a means to communicate data over longer distances on a chip. Furthermore, we find that realistic quantum error-correction circuits use a recursive structure that benefits from using teleportation for long-distance communication. We identify a set of important architectural building blocks necessary for constructing scalable communication and computation. Finally, we explore an actual layout scheme for recursive error correction, and demonstrate the exponential growth in communication costs with levels of recursion, and that teleportation limits those costs.

Implementation of nonlocal quantum swap operation on two entangled pairs

We propose a scheme for the implementation of nonlocal quantum swap operation on two spatially separated entangled pairs and we show that the operation can swap two qubits of these entangled pairs. We discuss the resources of the entangled qubits and classical communication bits required for the optimal implementation of the nonlocal quantum swap operation. We also put forward a scheme for probabilistic implementation of nonlocal swap operation via a nonmaximally entangled quantum channel. The probability of a successful nonlocal swap operation is obtained by introducing a collective unitary transformation.

Decoherence of the quantum gate in Milburn’s model of decoherence

We study the decoherence properties of a two-qubit quantum swap gate in Milburn's model of decoherence where the gate is realized by the quantum-dot system. We examine how the so-called intrinsic decoherence may degrade the gate purity and gate fidelity of the quantum swap gate and also present a potential source for the occurrence of Milburn's equation in the system of concern.

Atomic quantum state teleportation and swapping.

A set of protocols for atoms-photons and atoms-atoms quantum state teleportation and swapping utilizing Einstein-Podolsky-Rosen light is proposed. The protocols work for polarization quantum states of multiphoton light pulses and macroscopic samples of atoms, i.e., for continuous quantum variables. A simple free space interaction of polarized light with a spin polarized atomic ensemble is shown to suffice for these protocols. Feasibility of experimental realization using gas samples of atoms is analyzed.

Partial teleportation of entanglement in a noisy environment

Partial teleportation of entanglement is to teleport one particle of an entangled pair through a quantum channel. This is conceptually equivalent to quantum swapping. We consider the partial teleportation of entanglement in the noisy environment, employing the Werner-state representation of the noisy channel for the simplicity of calculation. To have the insight of the many-body teleportation, we introduce the measure of correlation information and study the transfer of the correlation information and entanglement. We find that the fidelity becomes smaller as the initial state is entangled more for a given entanglement of the quantum channel. The entangled channel transfers at least some of the entanglement to the final state.

Dynamics of nuclear spin measurement in a mesoscopic solid-state quantum computer

We study numerically the process of nuclear spin measurement in a solid-state quantum computer of the type proposed by Kane, by calculating the quantum dynamics of two coupled nuclear spins on 31P donors implanted in 28Si. We estimate the time of the `quantum swap operation' - the minimum measurement time required for the reliable transfer of quantum information from the nuclear spin subsystem to the electronic subsystem. Our calculations show that for realistic values of the parameters this time is of the order of swap~5 × 10-5 s. We also calculate the probability of error for typical values of the external noise.