Search results for "qubit"
showing 10 items of 279 documents
Deterministic quantum teleportation of photonic quantum bits by a hybrid technique.
2014
The continuous-variable teleportation of a discrete-variable, photonic qubit is deterministic and allows for faithful qubit transfer even with imperfect continuous-variable entangled states: for four qubits, the overall transfer fidelities all exceed the classical limit of teleportation. Quantum teleportation is one of the most important elementary protocols in quantum information processing. Previous studies have achieved quantum teleportation, but usually randomly and at low rates. Two groups reporting in this issue of Nature have used contrasting methods to achieve the same aim —more efficient quantum teleportation. Takeda et al. describe the experimental realization of fully determinist…
Entanglement transfer in a noisy cavity network with parity-deformed fields
2019
We investigate the effects of parity-deformed fields on the dynamics of entanglement transfer to distant noninteracting atomic qubits. These qubits are embedded in two distant lossy cavities connected by a leaky short-length fiber (or additional cavity). The process is studied within a single-excitation subspace, the parity-deformed cavity photons allowing the introduction of static local classical fields, which function as a control. The mechanism of state transfer is analyzed in comparison to the uncontrolled case. We find that the transfer evolution exhibits an asymmetry with respect to atom-field detuning, being sensitive to the sign of the detuning. Under a linear interaction controlle…
Quantum repeaters and quantum key distribution: analysis of secret key rates
2012
We analyze various prominent quantum repeater protocols in the context of long-distance quantum key distribution. These protocols are the original quantum repeater proposal by Briegel, D\"ur, Cirac and Zoller, the so-called hybrid quantum repeater using optical coherent states dispersively interacting with atomic spin qubits, and the Duan-Lukin-Cirac-Zoller-type repeater using atomic ensembles together with linear optics and, in its most recent extension, heralded qubit amplifiers. For our analysis, we investigate the most important experimental parameters of every repeater component and find their minimally required values for obtaining a nonzero secret key. Additionally, we examine in det…
Quantum teleportation of an optical qutrit
2017
Quantum teleportation is an important building block of quantum information processing. For practical applications, a quantum teleporter with the potential to include quantum error correction should be realized.
All-optical storage of a qubit encoded in an oscillator
2017
The efficient and reliable storage of quantum states plays a crucial role for the realization of quantum computation and communication. For example, in linear optics quantum computation as represented by the KLM scheme [1], quantum storage enables one to store intermediate “results” or to boost scalability and reliability of the computation. To employ quantum storage for quantum computation, the storage should be applicable to superposition states, including phase information of the superposition as well as the amplitude information of the state's coefficients. Some schemes exist for such storage using electron or nuclear spins [2]. However, an all-optical storage without the use of atoms o…
Single and two-qubit dynamics in circuit QED architectures
2008
In this paper we overview our researches on the generation and the control of entangled states in the framework of circuit quantum electrodynamics. Applications in the context of quantum computing and quantum information theory are discussed.
Quantum state transfer in imperfect artificial spin networks
2005
High-fidelity quantum computation and quantum state transfer are possible in short spin chains. We exploit a system based on a dispersive qubit-boson interaction to mimic XY coupling. In this model, the usually assumed nearest-neighbors coupling is no more valid: all the qubits are mutually coupled. We analyze the performances of our model for quantum state transfer showing how pre-engineered coupling rates allow for nearly optimal state transfer. We address a setup of superconducting qubits coupled to a microstrip cavity in which our analysis may be applied.
Diffusion and transfer of entanglement in an array of inductively coupled flux qubits
2007
A theoretical scheme to generate multipartite entangled states in a Josephson planar-designed architecture is reported. This scheme improves the one published in [Phys. Rev. B 74, 104503 (2006)] since it speeds up the generation of W entangled states in an MxN array of inductively coupled Josephson flux qubits by reducing the number of necessary steps. In addition, the same protocol is shown to be able to transfer the W state from one row to the other.
Heat flux and quantum correlations in dissipative cascaded systems
2015
We study the dynamics of heat flux in the thermalization process of a pair of identical quantum systems that interact dissipatively with a reservoir in a cascaded fashion. Despite that the open dynamics of the bipartite system $S$ is globally Lindbladian, one of the subsystems ``sees'' the reservoir in a state modified by the interaction with the other subsystem and hence it undergoes a non-Markovian dynamics. As a consequence, the heat flow exhibits a nonexponential time behavior which can greatly deviate from the case where each party is independently coupled to the reservoir. We investigate both thermal and correlated initial states of $S$ and show that the presence of correlations at th…
Mixed internal-external state approach for quantum computation with neutral atoms on atom chips
2006
We present a realistic proposal for the storage and processing of quantum information with cold Rb atoms on atom chips. The qubit states are stored in hyperfine atomic levels with long coherence time, and two-qubit quantum phase gates are realized using the motional states of the atoms. Two-photon Raman transitions are used to transfer the qubit information from the internal to the external degree of freedom. The quantum phase gate is realized in a double-well potential created by slowly varying dc currents in the atom chip wires. Using realistic values for all experimental parameters (currents, magnetic fields, ...) we obtain high gate fidelities (above 99.9%) in short operation times (~ 1…