arXiv subjects

C. J. Picken

Publications and source records attributed to C. J. Picken.

5 recordsLinked to original sources

arXiv2024

Demonstration of weighted graph optimization on a Rydberg atom array using local light-shifts

Neutral atom arrays have emerged as a versatile platform towards scalable quantum computation and optimization. In this paper we present demonstrations of solving maximum weighted independent set problems on a Rydberg atom array using annealing with local light-shifts. We verify the ability to prepare weighted graphs in 1D and 2D arrays, including embedding a five vertex non-unit disk graph using nine physical qubits and demonstration of a simple crossing gadget. We find common annealing ramps leading to preparation of the target ground state robustly over a substantial range of different graph weightings. This work provides a route to exploring large-scale optimization of non-planar weighted graphs relevant for solving relevant real-world problems.

quant-ph↗

arXiv2023

Laser Systems for High Fidelity Control and Entanglement of Neutral Atomic Qubits

We present new photonics and electronics packages recently developed by M Squared Lasers specifically tailored for scalable neutral atom quantum computing; a high power 1064 nm system for scalable qubit number, a phase locked system for high fidelity single qubit control, and robust cavity locked systems for high fidelity Rydberg operations. We attain driven coherence times competitive with current state-of-the-art for both ground state Raman and ground-Rydberg transitions without cavity filtering, providing an excellent platform for neutral atom quantum computing. These systems are benchmarked by creating entangled Bell states across 7 atom pairs, where we measure a peak raw fidelity of $F\ge0.88(2)$ and a peak SPAM corrected of $F_C\ge0.93(3)$ via a two-qubit $CZ$ gate.

physics.atom-ph↗

arXiv2018

Entanglement of neutral-atom qubits with long ground-Rydberg coherence times

We report results of a ground-state entanglement protocol for a pair of Cs atoms separated by 6~$μ$m, combining the Rydberg blockade mechanism with a two-photon Raman transitions to prepare the $\vertΨ^+\rangle=(\vert 10\rangle+\vert 01\rangle)/\sqrt{2}$ Bell state with a loss-corrected fidelity of 0.81(5), equal to the best demonstrated fidelity for atoms trapped in optical tweezers but without the requirement for dynamically adjustable interatomic spacing. Qubit state coherence is also critical for quantum information applications, and we characterise both ground-state and ground-Rydberg dephasing rates using Ramsey spectroscopy. We demonstrate transverse dephasing times $T_2^*=10(1)$~ms and $T_2'=0.14(1)$~s for the qubit levels and achieve long ground-Rydberg coherence times of $T_2^*=17(2)~μ$s as required for implementing high-fidelity multi-qubit gate sequences where a control atom remains in the Rydberg state while applying local operations on neighbouring target qubits.

quant-ph↗

arXiv2018

Sub-kHz excitation lasers for Quantum Information Processing with Rydberg atoms

Quantum information processing using atomic qubits requires narrow linewidth lasers with long-term stability for high fidelity coherent manipulation of Rydberg states. In this paper, we report on the construction and characterization of three continuous-wave (CW) narrow linewidth lasers stabilized simultaneously to an ultra-high finesse Fabry-Perot cavity made of ultra-low expansion (ULE) glass, with a tunable offset-lock frequency. One laser operates at 852~nm while the two locked lasers at 1018~nm are frequency doubled to 509~nm for excitation of $^{133}$Cs atoms to Rydberg states. The optical beatnote at 509~nm is measured to be 260(5)~Hz. We present measurements of the offset between the atomic and cavity resonant frequencies using electromagnetically induced transparency (EIT) for high-resolution spectroscopy on a cold atom cloud. The long-term stability is determined from repeated spectra over a period of 20 days yielding a linear frequency drift of $\sim1$~Hz/s.

physics.atom-ph↗

arXiv2017

Single Atom Imaging with an sCMOS camera

Single atom imaging requires discrimination of weak photon count events above background and has typically been performed using either EMCCD cameras, photomultiplier tubes or single photon counting modules. sCMOS provides a cost effective and highly scalable alternative to other single atom imaging technologies, offering fast readout and larger sensor dimensions. We demonstrate single atom resolved imaging of two site-addressable single atom traps separated by 10~$μ$m using an sCMOS camera, offering a competitive signal-to-noise ratio at intermediate count rates to allow high fidelity readout discrimination (error $<10^{-6}$) and sub-$μ$m spatial resolution for applications in quantum technologies.

physics.atom-ph↗