1,287 research outputs found
Generation of cluster states
We propose two schemes for the generation of the cluster states. One is based
on cavity quantum electrodynamics (QED) techniques. The scheme only requires
resonant interactions between two atoms and a single-mode cavity. The
interaction time is very short, which is important in view of decoherence.
Furthermore, we also discuss the cavity decay and atomic spontaneous emission
case. The other is based on atomic ensembles. The scheme has inherent fault
tolerance function and is robust to realistic noise and imperfections. All the
facilities used in our schemes are well within the current technology.Comment: Complete rewite version, adding the main results of quant-ph/0511045.
7 pages and 3 figure
Robust nonadiabatic geometric quantum computation by dynamical correction
Besides the intrinsic noise resilience property, nonadiabatic geometric
phases are of the fast evolution nature, and thus can naturally be used in
constructing quantum gates with excellent performance, i.e., the so-called
nonadiabatic geometric quantum computation (NGQC). However, previous
single-loop NGQC schemes are sensitive to the operational control error, i.e.,
the error, due to the limitations of the implementation. Here, we propose a
robust scheme for NGQC combining with the dynamical correction technique, which
still uses only simplified pulses, and thus being experimental friendly. We
numerically show that our scheme can greatly improve the gate robustness in
previous protocols, retaining the intrinsic merit of geometric phases.
Furthermore, to fight against the dephasing noise, due to the error, we can
incorporate the decoherence-free subspace encoding strategy. In this way, our
scheme can be robust against both types of errors. Finally, we also propose how
to implement the scheme with encoding on superconducting quantum circuits with
experimentally demonstrated technology. Therefore, due to the intrinsic
robustness, our scheme provides a promising alternation for the future scalable
fault-tolerant quantum computation.Comment: 6 pages, 5 figure
An Experimental Proposal to Test Dynamic Quantum Non-locality with Single-Atom Interferometry
Quantum non-locality based on the well-known Bell inequality is of kinematic
nature. A different type of quantum non-locality, the non-locality of the
quantum equation of motion, is recently put forward with connection to the
Aharonov-Bohm effect [Nature Phys. 6, 151 (2010)]. Evolution of the
displacement operator provides an example to manifest such dynamic quantum
non-locality. We propose an experiment using single-atom interferometry to test
such dynamic quantum non-locality. We show how to measure evolution of the
displacement operator with clod atoms in a spin-dependent optical lattice
potential and discuss signature to identify dynamic quantum non-locality under
a realistic experimental setting.Comment: 4 page
Teleportation for atomic entangled state by entanglement swapping with separate measurements in cavity QED
Experimentally feasible scheme for teleportation of atomic entangled state
via entanglement swapping is proposed in cavity quantum electrodynamics (QED)
without joint Bell-state measurement (BSM). In the teleportation processes the
interaction between atoms and a single-mode nonresonant cavity with the
assistance of a strong classical driving field substitute the joint
measurements. The discussion of the scheme indicates that it can be realized by
current technologies.Comment: 5 pages, no figur
Time-optimal universal quantum gates on superconducting circuits
Decoherence is inevitable when manipulating quantum systems. It decreases the
quality of quantum manipulations and thus is one of the main obstacles for
large-scale quantum computation, where high-fidelity quantum gates are needed.
Generally, the longer a gate operation is, the more decoherence-induced gate
infidelity will be. Therefore, how to shorten the gate time becomes an urgent
problem to be solved. To this end, time-optimal control based on solving the
quantum brachistochrone equation is a straightforward solution. Here, based on
time-optimal control, we propose a scheme to realize universal quantum gates on
superconducting qubits in a two-dimensional square lattice configuration, and
the two-qubit gate fidelity approaches 99.9\%. Meanwhile, we can further
accelerate the Z-axis gate considerably by adjusting the detuning of the
external driving. Finally, in order to reduce the influence of the dephasing
error, decoherence-free subspace encoding is also incorporated in our physical
implementation. Therefore, we present a fast quantum scheme which is promising
for large-scale quantum computation.Comment: v2 accepte
Robust interface between flying and topological qubits
Hybrid architectures, consisting of conventional and topological qubits, have
recently attracted much attention due to their capability in consolidating the
robustness of topological qubits and the universality of conventional qubits.
However, these two kinds of qubits are normally constructed in significantly
different energy scales, and thus this energy mismatch is a major obstacle for
their coupling that supports the exchange of quantum information between them.
Here, we propose a microwave photonic quantum bus for a direct strong coupling
between the topological and conventional qubits, in which the energy mismatch
is compensated by the external driving field via the fractional ac Josephson
effect. In the framework of tight-binding simulation and perturbation theory,
we show that the energy splitting of the topological qubits in a finite length
nanowire is still robust against local perturbations, which is ensured not only
by topology, but also by the particle-hole symmetry. Therefore, the present
scheme realizes a robust interface between the flying and topological qubits.
Finally, we demonstrate that this quantum bus can also be used to generate
multipartitie entangled states with the topological qubits.Comment: Accepted for publication in Scientific Report
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