35 research outputs found
Simple preparation of Bell and GHZ states using ultrastrong-coupling circuit QED
The ability to entangle quantum systems is crucial for many applications in
quantum technology, including quantum communication and quantum computing.
Here, we propose a new, simple, and versatile setup for deterministically
creating Bell and Greenberger-Horne-Zeilinger (GHZ) states between photons of
different frequencies in a two-step protocol. The setup consists of a quantum
bit (qubit) coupled ultrastrongly to three photonic resonator modes. The only
operations needed in our protocol are to put the qubit in a superposition
state, and then tune its frequency in and out of resonance with sums of the
resonator-mode frequencies. By choosing which frequency we tune the qubit to,
we select which entangled state we create. We show that our protocol can be
implemented with high fidelity using feasible experimental parameters in
state-of-the-art circuit quantum electrodynamics. One possible application of
our setup is as a node distributing entanglement in a quantum network.Comment: 15 pages, 7 figure
Atomic quantum state transferring and swapping via quantum Zeno dynamics
In this paper, we first demonstrate how to realize quantum state transferring
(QST) from one atom to another based on quantum Zeno dynamics. Then, the QST
protocol is generalized to realize the quantum state swapping (QSS) between two
arbitrary atoms with the help of a third one. Furthermore, we also consider the
QSS within a quantum network. The influence of decoherence is analyzed by
numerical calculation. The results demonstrate that the protocols are robust
against cavity decay.Comment: To appear in J. Opt. Soc. Am. B (JOSAB
High-fidelity interconversion between Greenberger-Horne-Zeilinger and states through Floquet-Lindblad engineering in Rydberg atom arrays
Greenberger-Horne-Zeilinger and W states feature genuine tripartite
entanglement that cannot be converted into each other by local operations and
classical communication. Here, we present a dissipative protocol for
deterministic interconversion between Greenberger-Horne-Zeilinger and W states
of three neutral Rb atoms arranged in an equilateral triangle of a
two-dimensional array. With three atomic levels and diagonal van der Waals
interactions of Rydberg atoms, the interconversion between tripartite entangled
states can be efficiently accomplished in the Floquet-Lindblad framework
through the periodic optical pump and dissipation engineering. We evaluate the
feasibility of the existing methodology using the experimental parameters
accessible to current neutral-atom platforms. We find that our scheme is robust
against typical noises, such as laser phase noise and geometric imperfections
of the atom array. In addition, our scheme can integrate the Gaussian soft
quantum control technique, which further reduces the overall conversion time
and increases the resilience to timing errors and interatomic distance
fluctuations. The high-fidelity and robust tripartite entanglement
interconversion protocol provides a route to save physical resources and
enhance the computational efficiency of quantum networks formed by neutral-atom
arrays.Comment: 18 pages, 14 figures, accepted by Physical Review Applie
Quantum logic and entanglement by neutral Rydberg atoms: methods and fidelity
Quantum gates and entanglement based on dipole-dipole interactions of neutral
Rydberg atoms are relevant to both fundamental physics and quantum information
science. The precision and robustness of the Rydberg-mediated entanglement
protocols are the key factors limiting their applicability in experiments and
near-future industry. There are various methods for generating entangling gates
by exploring the Rydberg interactions of neutral atoms, each equipped with its
own strengths and weaknesses. The basics and tricks in these protocols are
reviewed, with specific attention paid to the achievable fidelity and the
robustness to the technical issues and detrimental innate factors.Comment: 57 pages, 10 figure