Multiatom entanglement in cold Rydberg mixtures

Physical Review Letters, 2009

We present an efficient method for producing N particle entangled states using Rydberg blockade interactions. Optical excitation of Rydberg states that interact weakly, yet have a strong coupling to a second control state is used to achieve state dependent qubit rotations in small ensembles. On the basis of quantitative calculations, we predict that an entangled quantum superposition state of eight atoms can be produced with a fidelity of 84% in cold Rb atoms.

Advances In Atomic, Molecular, and Optical Physics, 2012

Over the past few years we have built an apparatus to demonstrate the entanglement of neutral Rb atoms at optically resolvable distances using the strong interactions between Rydberg atoms. Here we review the basic physics involved in this process: loading of single atoms into individual traps, state initialization, state readout, single atom rotations, blockade-mediated manipulation of Rydberg atoms, and demonstration of entanglement.

Journal of Physics: Conference Series

We investigated two Rydberg atoms successively passing a vacuum or a thermal cavity taking into account the detuning. The atoms was assumed to be initially prepared in the Bell types entangled atomic states. Calculating the negativity we investigated the dynamics of atom-atom entanglement both for the vacuum and the thermal field. The special features of negativity behavior have been studied comprehensively foe small and large values of detunings. For thermal field and small detunings we established the effect of sudden death and birth of entanglement.

2010

We report on our recent progress on the manipulation of single rubidium atoms trapped in optical tweezers and the generation of entanglement between two atoms, each individually trapped in neighboring tweezers. To create an entangled state of two atoms in their ground states, we make use of the Rydberg blockade mechanism. The degree of entanglement is measured using global rotations of the internal states of both atoms. Such internal state rotations on a single atom are demonstrated with a high fidelity.

2017

We investigated the entanglement between two identical two-level Rydberg atoms successively passing cavity and interacting with one-mode field through a one-photon and degenerate two-photon processes. For two-photon interaction, we focused our attention on the study of atomic entanglement dynamics in the presence of the Stark shift and initial atomic coherence. For one-photon case we discussed the influence of atomic coherence, detuning and cavity thermal photons on the entanglement dynamics for entangled initial atomic states.

Physical Review Letters, 2008

We propose to apply stimulated adiabatic passage to transfer atoms from their ground state into Rydberg excited states. Atoms a few micrometers apart experience a dipole-dipole interaction among Rydberg states that is strong enough to shift the atomic resonance and inhibit excitation of more than a single atom. We show that the adiabatic passage in the presence of this interaction between two atoms leads to robust creation of maximally entangled states and to two-bit quantum gates. For many atoms, the excitation blockade leads to an effective implementation of collectivespin and Jaynes-Cummings-like Hamiltonians, and we show that the adiabatic passage can be used to generate collective Jx = 0 eigenstates and Greenberger-Horne-Zeilinger states of tens of atoms.

Physical Review A

Based on Lyapunov control, a scheme is proposed to accelerate the dissipation dynamics for the generation of high-fidelity entanglement between two Rydberg atoms in the context of cavity quantum electrodynamics (QED). We first use the quantum Zeno dynamics and Rydberg antiblockade to find a unique steady state (two-atom singlet state) for the system. Then, applying additional coherent control (ACC) fields to improve the evolution speed of the dissipative system. The ACC fields are designed based on the target state and they vanish gradually along with increasing of the fidelity thus the system is guaranteed to be finally stable. Besides, the current accelerated scheme is checked to be robust against systematic and amplitude-noise errors.

Physical Review A, 2014

We propose a scheme that employs dissipation to deterministically generate entanglement in an ensemble of strongly interacting Rydberg atoms. With a combination of microwave driving between different Rydberg levels and a resonant laser coupling to a short lived atomic state, the ensemble can be driven towards a dark steady state that entangles all atoms. The long-range resonant dipole-dipole interaction between different Rydberg states extends the entanglement beyond the van der Walls interaction range with perspectives for entangling large and distant ensembles.

Physical Review Letters, 2019

We demonstrate high fidelity two-qubit Rydberg blockade and entanglement in a two-dimensional qubit array. The qubit array is defined by a grid of blue detuned lines of light with 121 sites for trapping atomic qubits. Improved experimental methods have increased the observed Bell state fidelity to F Bell = 0.86(2). Accounting for errors in state preparation and measurement (SPAM) we infer a fidelity of F −SPAM Bell = 0.88. Accounting for errors in single qubit operations we infer that a Bell state created with the Rydberg mediated CZ gate has a fidelity of F C Z Bell = 0.89. Comparison with a detailed error model based on quantum process matrices indicates that finite atom temperature and laser noise are the dominant error sources contributing to the observed gate infidelity.

Controlling quantum entanglement between parts of a many-body system is the key to unlocking the power of quantum information processing for applications such as quantum computation, highprecision sensing, and simulation of many-body physics. Spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform given their long coherence times and our ability to control them with magneto-optical fields, but creating strong coherent coupling between spins has been challenging. We demonstrate a Rydberg-dressed ground-state blockade that provides a strong tunable interaction energy (~1 MHz in units of Planck's constant) between spins of individually trapped cesium atoms. With this interaction we directly produce Bell-state entanglement between two atoms with a fidelity >= 81(2)%, excluding atom loss events, and >= 60(3)% when loss is included.