No Arabic abstract
We construct a scheme for the preparation, pairwise entanglement via exchange interaction, manipulation, and measurement of individual group-II-like neutral atoms (Yb, Sr, etc.). Group-II-like atoms proffer important advantages over alkali metals, including long-lived optical-transition qubits that enable fast manipulation and measurement. Our scheme provides a promising approach for producing weighted graph states, entangled resources for quantum communication, and possible application to fundamental tests of Bell inequalities that close both detection and locality loopholes.
Quantum information can be processed using large ensembles of ultracold and trapped neutral atoms, building naturally on the techniques developed for high-precision spectroscopy and metrology. This article reviews some of the most important protocols for universal quantum logic with trapped neutrals, as well as the history and state-of-the-art of experimental work to implement these in the laboratory. Some general observations are made concerning the different strategies for qubit encoding, transport and interaction, including tradeoffs between decoherence rates and the likelihood of twoqubit gate errors. These tradeoffs must be addressed through further refinements of logic protocols and trapping technologies before one can undertake the design of a generalpurpose neutral-atom quantum processor.
We demonstrate a SWAP gate between laser-cooled ions in a segmented microtrap via fast physical swapping of the ion positions. This operation is used in conjunction with qubit initialization, manipulation and readout, and with other types of shuttling operations such as linear transport and crystal separation and merging. Combining these operations, we perform quantum process tomography of the SWAP gate, obtaining a mean process fidelity of 99.5(5)%. The swap operation is demonstrated with motional excitations below 0.05(1)~quanta for all six collective modes of a two-ion crystal, for a process duration of 42~$mu$s. Extending these techniques to three ions, we reverse the order of a three-ion crystal and reconstruct the truth table for this operation, resulting in a mean process fidelity of 99.96(13)% in the logical basis.
Atomic systems, ranging from trapped ions to ultracold and Rydberg atoms, offer unprecedented control over both internal and external degrees of freedom at the single-particle level. They are considered among the foremost candidates for realizing quantum simulation and computation platforms that can outperform classical computers at specific tasks. In this work, we describe a realistic experimental toolbox for quantum information processing with neutral alkaline-earth-like atoms in optical tweezer arrays. In particular, we propose a comprehensive and scalable architecture based on a programmable array of alkaline-earth-like atoms, exploiting their electronic clock states as a precise and robust auxiliary degree of freedom, and thus allowing for efficient all-optical one- and two-qubit operations between nuclear spin qubits. The proposed platform promises excellent performance thanks to high-fidelity register initialization, rapid spin-exchange gates and error detection in readout. As a benchmark and application example, we compute the expected fidelity of an increasing number of subsequent SWAP gates for optimal parameters, which can be used to distribute entanglement between remote atoms within the array.
We present the realization of a ultra fast shutter for optical fields, which allows to preserve a generic polarization state, based on a self-stabilized interferometer. It exhibits high (or low) transmittivity when turned on (or inactive), while the fidelity of the polarization state is high. The shutter is realized through two beam displacing prisms and a longitudinal Pockels cell. This can represent a useful tool for controlling light-atom interfaces in quantum information processing.
We show how optically-driven coupled quantum dots can be used to prepare maximally entangled Bell and Greenberger-Horne-Zeilinger states. Manipulation of the strength and duration of the selective light-pulses needed for producing these highly entangled states provides us with crucial elements for the processing of solid-state based quantum information. Theoretical predictions suggest that several hundred single quantum bit rotations and Controlled-Not gates could be performed before decoherence of the excitonic states takes place.