Scheme For Quantum State Transfer Research Articles

Quantum teleportation-based state transfer of photon polarization into a carbon spin in diamond

Quantum teleportation is a key principle for quantum information technology. It permits the transfer of quantum information into an otherwise inaccessible space, while also permitting the transfer of photon information into a quantum memory without revealing or destroying the stored quantum information. Here, we show reliable quantum state transfer of photon polarization into a carbon isotope nuclear spin coupled to a nitrogen-vacancy center in diamond based on photon-electron Bell state measurement by photon absorption. The carbon spin is first entangled with the electron spin, which is then permitted to absorb a photon into a spin-orbit correlated eigenstate. Detection of the electron after relaxation into the spin ground state allows post-selected transfer of arbitrary photon polarization into the carbon memory. The quantum state transfer scheme allows individual addressing of integrated quantum memories to realize scalable quantum repeaters for long-haul quantum communications, and distributed quantum computers for large-scale quantum computation and metrology.

Low temperature dynamics of netral atoms for quantum logic

We study from the point of view of quantum logic the properties of the collective oscillations of two Rydberg atoms in two harmonic traps. The difference in the frequency of two normal modes of motion expands with the difference in the mass of the two atoms. The probability of excitation of the motional quanta due to the strong dipole-dipole interaction can be made to be sufficiently small. Based on the normal modes of motion we present a scheme for quantum state transfer which is useful for quantum information process and for precision spectroscopy of atoms that lack suitable transitions for efficient laser cooling, internal state preparation, and detection.

Virtual-Excitation Induced High-Dimensional State Transfer in a Quantum Network

We propose a scheme for quantum state transfer within the high-dimensional state subspaces between any two nodes in a quantum network. The states are encoded in the collective ground states of multiple atoms. The transfer processes are controlled by only applying external laser pulses. The prominent feature of the scheme is that the state transfer of any dimension can be achieved through virtually coupling all the excitations of the total system.

Parity-based mirror inversion for efficient quantum state transfer and computation in nearest-neighbor arrays

We introduce an efficient scheme for quantum state transfer that uses a parity-based mirror inversion technique. We design efficient circuits for implementing mirror inversion in Ising ${\mathbit{\ensuremath{\sigma}}}_{\mathbf{X}}{\mathbit{\ensuremath{\sigma}}}_{\mathbf{X}}$ and ${\mathbit{\ensuremath{\sigma}}}_{\mathbf{Y}}{\mathbit{\ensuremath{\sigma}}}_{\mathbf{Y}}$ coupled systems and show how to analytically solve for system parameters to implement the operation in these systems. The key feature of our scheme is a three-qubit parity gate, which we design as a two-control one-target qubit gate. The parity gate operation is implemented by only varying a single control parameter of the system Hamiltonian and the difficulty of implementing this gate is equivalent to that of a controlled-not gate in a two-qubit system. By applying a sequence of $N+1$ parity-based controlled-unitary operations between nearest-neighbor qubits, where all qubits in an $N$-qubit chain function either as controls or targets, we are able to reverse the order of all qubits along the array. These operations are accomplished by varying only a single control parameter per data qubit. The control parameter depends on the physical system under consideration and on the choice of the designer. Since every qubit participates in the mirror-inversion process functioning either as a control or target, all nearest-neighbor couplings are used. Therefore, we do not need additional measures to cancel the effect of any unwanted interactions and the quantum cost of our scheme does not increase in systems that do not have the ability shut off couplings. Moreover, our scheme does not require additional ancillas, nor does it use a pre-engineered mirror-periodic Hamiltonian to govern the evolution of the system. Using our mirror inversion scheme, we also show how to implement a swap gate between two arbitrary remote qubits, move a block of qubits, and implement efficient computing between two remote qubits in nearest-neighbor layouts.

Robust quantum state transfer between a Cooper-pair box and diamond nitrogen-vacancy centers

We propose a potentially practical scheme for quantum state transfer between a Cooper-pair box circuit and an electron spin ensemble of diamond nitrogen-vacancy (NV) centers. Both subsystems are placed into a common circuit QED and can be modeled as effective three-level subsystems under the appropriate external biases. Due to significant suppression of the photon decay, the robust state transfer between the two subsystems can be accomplished by using the technique of stimulated Raman adiabatic passage by individual microwave pulses, where a superconducting coplanar resonator serves as the quantum data bus. Numerical simulations show that the present scheme could offer a viable route towards robust quantum state transfer in hybrid solid-state systems.

Optimal transfer of an unknown state via a bipartite quantum operation

A fundamental task in quantum information science is to transfer an unknown state from particle A to particle B (often in remote space locations) by using a bipartite quantum operation . We suggest the power of for quantum state transfer (QST) to be the maximal average probability of QST over the initial states of particle B and the identifications of the state vectors between A and B. We find the QST power of a bipartite quantum operations satisfies four desired properties between two d-dimensional Hilbert spaces. When A and B are qubits, the analytical expressions of the QST power is given. The numerical result on a QST scheme via a quantum wire shows the necessity to optimize the average fidelity. In particular, we obtain the exact results of the QST power for a general two-qubit unitary transformation, and we find a necessary and sufficient condition for the two-qubit unitary gates with perfect QST.

Low temperature dynamics of netral atoms for quantum logic

We study from the point of view of quantum logic the properties of the collective oscillations of two Rydberg atoms in two harmonic traps. The difference in the frequency of two normal modes of motion expands with the difference in the mass of the two atoms. The probability of excitation of the motional quanta due to the strong dipole-dipole interaction can be made to be sufficiently small. Based on the normal modes of motion we present a scheme for quantum state transfer which is useful for quantum information process and for precision spectroscopy of atoms that lack suitable transitions for efficient laser cooling, internal state preparation, and detection.

Environment-mediated quantum state transfer

We propose a scheme for quantum state transfer (QST) between two qubits, which is based on their individual interaction with a common boson environment. The corresponding single-mode spin-boson Hamiltonian is solved by mapping it into a wave propagation problem in a semi-infinite ladder and the fidelity is obtained. High fidelity occurs when the qubits are equally coupled to the boson while the fidelity becomes smaller for nonsymmetric couplings. The complete phase diagram for such an arbitrary QST mediated by bosons is discussed.

Multiatom and resonant interaction scheme for quantum state transfer and logical gates between two remote cavities via an optical fiber

A system consisting of two single-mode cavities spatially separated and connected by an optical fiber and multiple two-level atoms trapped in the cavities is considered. If the atoms resonantly and collectively interact with the local cavity fields but there is no direct interaction between the atoms, we show that an ideal quantum state transfer and highly reliable quantum swap, entangling, and controlled-Z gates can be deterministically realized between the distant cavities. We find that the operation of state transfer and swap, entangling, and controlled-Z gates can be greatly speeded up as number of the atoms in the cavities increases. We also notice that the effects of spontaneous emission of atoms and photon leakage out of cavity on the quantum processes can also be greatly diminished in the multiatom case.