Logical quantum processor based on reconfigurable atom arrays

• Published in: Nature (London) Vol. 626; no. 7997; pp. 58 - 65
• Main Authors: Bluvstein, Dolev, Evered, Simon J., Geim, Alexandra A., Li, Sophie H., Zhou, Hengyun, Manovitz, Tom, Ebadi, Sepehr, Cain, Madelyn, Kalinowski, Marcin, Hangleiter, Dominik, Bonilla Ataides, J. Pablo, Maskara, Nishad, Cong, Iris, Gao, Xun, Sales Rodriguez, Pedro, Karolyshyn, Thomas, Semeghini, Giulia, Gullans, Michael J., Greiner, Markus, Vuletić, Vladan, Lukin, Mikhail D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2024; Nature Publishing Group
• Subjects: 639/624/1107/1110; 639/766/36; 639/766/483/2802; 639/766/483/481; Algorithms; Arrays; Coding; Color; Error correction; Error correction & detection; Error detection; Fault tolerance; Field programmable gate arrays; Gates (circuits); Humanities and Social Sciences; Hypercubes; Logic circuits; Microprocessors; multidisciplinary; Quantum computing; Quantum entanglement; Qubits (quantum computing); Reconfiguration; Science; Science & Technology - Other Topics; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-023-06927-3

Suppressing errors is the central challenge for useful quantum computing
1
, requiring quantum error correction (QEC)
2
–
6
for large-scale processing. However, the overhead in the realization of error-corrected ‘logical’ qubits, in which information is encoded across many physical qubits for redundancy
2
–
4
, poses substantial challenges to large-scale logical quantum computing. Here we report the realization of a programmable quantum processor based on encoded logical qubits operating with up to 280 physical qubits. Using logical-level control and a zoned architecture in reconfigurable neutral-atom arrays
7
, our system combines high two-qubit gate fidelities
8
, arbitrary connectivity
7
,
9
, as well as fully programmable single-qubit rotations and mid-circuit readout
10
–
15
. Operating this logical processor with various types of encoding, we demonstrate improvement of a two-qubit logic gate by scaling surface-code
6
distance from
d
 = 3 to
d
 = 7, preparation of colour-code qubits with break-even fidelities
5
, fault-tolerant creation of logical Greenberger–Horne–Zeilinger (GHZ) states and feedforward entanglement teleportation, as well as operation of 40 colour-code qubits. Finally, using 3D [[8,3,2]] code blocks
16
,
17
, we realize computationally complex sampling circuits
18
with up to 48 logical qubits entangled with hypercube connectivity
19
with 228 logical two-qubit gates and 48 logical CCZ gates
20
. We find that this logical encoding substantially improves algorithmic performance with error detection, outperforming physical-qubit fidelities at both cross-entropy benchmarking and quantum simulations of fast scrambling
21
,
22
. These results herald the advent of early error-corrected quantum computation and chart a path towards large-scale logical processors.
A programmable quantum processor based on encoded logical qubits operating with up to 280 physical qubits is described, in which improvement of algorithmic performance using a variety of error-correction codes is enabled.