Multi-qubit entanglement and algorithms on a neutral-atom quantum computer

Graham, Trent; Song, Yunheung; Scott, Jillian J.; Poole, Cody; Phuttitarn, L; Jooya, K.; Eichler, Paul; Xun, Jiang; Marra, Alphonse; Grinkemeyer, Brandon; Kwon, Minho; Ebert, Matthew; Cherek, J; Lichtman, Martin; Gillette, M; Gilbert, J; Bowman, D; Ballance, T; Campbell, Colin; Dahl, Edward D.; Crawford, Ophelia; Blunt, Nick S.; Rogers, B; Noël, Thomas; Saffman, M.

doi:10.1038/s41586-022-04603-6

Cited by 274 publications

(128 citation statements)

References 46 publications

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“…To offer better flexibility, the mixer operator pool should include multi- qubit operators beyond those supported on nearest neighbors. It will thus be easier to demonstrate ADAPT-QAOA on platforms with less limitation on entangling operations between arbitrary pairs of qubits, such as trapped ion systems [54][55][56] and Rydberg atoms [57][58][59].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

How Much Entanglement Do Quantum Optimization Algorithms Require?

Chen¹,

Zhu²,

Liu³

et al. 2022

Preprint

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Many classical optimization problems can be mapped to finding the ground states of diagonal Ising Hamiltonians, for which variational quantum algorithms such as the Quantum Approximate Optimization Algorithm (QAOA) provide heuristic methods.Because the solutions of such classical optimization problems are necessarily product states, it is unclear how entanglement affects their performance.An Adaptive Derivative-Assembled Problem-Tailored (ADAPT) variation of QAOA improves the convergence rate by allowing entangling operations in the mixer layers whereas it requires fewer CNOT gates in the entire circuit. In this work, we study the entanglement generated during the execution of ADAPT-QAOA. Through simulations of the weighted Max-Cut problem, we show that ADAPT-QAOA exhibits substantial flexibility in entangling and disentangling qubits. By incrementally restricting this flexibility, we find that a larger amount of entanglement entropy at earlier stages coincides with faster convergence at later stages. In contrast, while the standard QAOA quickly generates entanglement within a few layers, it cannot remove excess entanglement efficiently. Our results offer implications for favorable features of quantum optimization algorithms.

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Section: Conclusion and Discussionmentioning

confidence: 99%

How Much Entanglement Do Quantum Optimization Algorithms Require?

Chen¹,

Zhu²,

Liu³

et al. 2022

Preprint

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show abstract

“…The scalability and robustness of the cooling protocol is promising for expansion to arrays of tweezer traps, and we demonstrate simultaneous cooling of Rb atoms in an array of four tweezers. Application of our RSC protocol to dual-species arrays of Rb and Cs atoms [19] would allow initialisation of both species in the motional ground-state, improving the fidelity of tweezer-based quantum logic gates [94,95]. In addition, this would realise an ideal system for implementing the mid-circuit measurements [22] that are necessary for quantum error correction schemes [96].…”

Section: Discussionmentioning

confidence: 99%

Preparation of $^{87}$Rb and $^{133}$Cs in the motional ground state of a single optical tweezer

Spence,

Brooks,

Ruttley

et al. 2022

Preprint

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We report simultaneous Raman sideband cooling of a single 87 Rb atom and a single 133 Cs atom held in separate optical tweezers at 814 nm and 938 nm, respectively. Starting from outside the Lamb-Dicke regime, after 45 ms of cooling we measure probabilities to occupy the three-dimensional motional ground state of 0.86 +0.03 −0.04 for Rb and 0.95 +0.03 −0.04 for Cs. Our setup overlaps the Raman laser beams used to cool Rb and Cs, reducing hardware requirements by sharing equipment along the same beam path. The cooling protocol is scalable, and we demonstrate cooling of single Rb atoms in an array of four tweezers. After motional ground-state cooling, a 938 nm tweezer is translated to overlap with a 814 nm tweezer so that a single Rb and a single Cs atom can be transferred into a common 1064 nm trap. By minimising the heating during the merging and transfer, we prepare the atoms in the relative motional ground state with an efficiency of 0.81 +0.08 −0.08 . This is a crucial step towards the association of arrays of single RbCs molecules confined in optical tweezers.

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“…This is the result of advances over the past two decades in creating lowentropy arrays of single atoms, which have made optical trap arrays ubiquitous in quantum science. However, the optical setups for creating these traps are often complicated, space-consuming, and expensive, requiring active electro-optical devices such as liquid crystal spatial light modulators (SLMs) [3], acousto-optic deflectors (AODs) [4], and digital micromirror devices (DMDs) [5]. In response to this experimental overhead, we propose a simple method of creating optical trap arrays using only passive components, consisting of a mask with a custom transmission pattern and a 4f imaging setup with a Fourier plane iris for spatial filtering.…”

Section: Introductionmentioning

confidence: 99%

A simple, passive design for large optical trap arrays for single atoms

Huft,

Song,

Graham

et al. 2022

Preprint

Self Cite

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We present an approach for trapping cold atoms in a 2D optical trap array generated with a novel 4f filtering scheme and custom transmission mask without any active device. The approach can be used to generate arrays of bright or dark traps, or both simultaneously with a single wavelength for forming two-species traps. We demonstrate the design by creating a 2D array of 1225 dark trap sites, where single Cs atoms are loaded into regions of near-zero intensity in an approximately Gaussian profile trap. Moreover, we demonstrate a simple solution to the problem of out-of-focus trapped atoms, which occurs due to the Talbot effect in periodic optical lattices. Using a high power yet low cost spectrally and spatially broadband laser, out-of-focus interference is mitigated, leading to near perfect removal of Talbot plane traps.

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Multi-qubit entanglement and algorithms on a neutral-atom quantum computer

Cited by 274 publications

References 46 publications

How Much Entanglement Do Quantum Optimization Algorithms Require?

How Much Entanglement Do Quantum Optimization Algorithms Require?

Preparation of $^{87}$Rb and $^{133}$Cs in the motional ground state of a single optical tweezer

A simple, passive design for large optical trap arrays for single atoms

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