Quantum error correction below the surface code threshold

• Main Authors: Acharya, Rajeev, Aleiner, Igor, Andersen, Trond I, Ansmann, Markus, Arute, Frank, Arya, Kunal, Asfaw, Abraham, Atalaya, Juan, Bacon, Dave, Bilmes, Alexander, Bortoli, Gina, Bourassa, Alexandre, Bovaird, Jenna, Brill, Leon, Browne, David A, Burger, Tim, Bushnell, Nicholas, Cabrera, Anthony, Chang, Hung-Shen, Chik, Desmond, Collins, Roberto, Crook, Alexander L, Curtin, Ben, Davies, Alex, Donohoe, Paul, Drozdov, Ilya, Dunsworth, Andrew, Elzouka, Mahmoud, Farhi, Edward, Gasca, Robert, Genois, Élie, Giang, William, Graumann, Dietrich, Greene, Alex, Gross, Jonathan A, Habegger, Steve, Hall, John, Holland, George, Ioffe, Lev B, Jones, Cody, Kafri, Dvir, Klots, Andrey R, Kreikebaum, John Mark, Lacroix, Nathan, Landhuis, David, Lange-Dei, Tiano, Guevel, Loïck Le, Lee, Kenny, Lensky, Yuri D, Liu, Wayne, Locharla, Aditya, Lunt, Aaron, Martin, Steven, McClean, Jarrod R, McEwen, Matt, Meeks, Seneca, Mi, Xiao, Miao, Kevin C, Montazeri, Shirin, Morvan, Alexis, Movassagh, Ramis, Mruczkiewicz, Wojciech, Neeley, Matthew, Neill, Charles, Nersisyan, Ani, Neven, Hartmut, Newman, Michael, Ng, Jiun How, Opremcak, Alex, Ottosson, Kristoffer, Petukhov, Andre, Platt, John, Pryadko, Leonid P, Ramachandran, Ganesh, Reagor, Matthew J, Rhodes, David M, Rosenberg, Eliott, Rosenfeld, Emma, Roushan, Pedram, Rubin, Nicholas C, Sankaragomathi, Kannan, Satzinger, Kevin J, Senior, Andrew W, Shearn, Michael J, Small, Spencer, Smelyanskiy, Vadim, Sterling, George, Sztein, Alex, Torunbalci, M. Mert, Vaishnav, Abeer, Vdovichev, Sergey, Vidal, Guifre, Ware, Brayden, Xing, Cheng, Yao, Z. Jamie, Yeh, Ping, Ying, Bicheng, Young, Grayson, Zalcman, Adam, Zobrist, Nicholas
• Format: Journal Article
• Language: English
• Published: 24.08.2024
• Subjects: Physics - Quantum Physics
• DOI: 10.48550/arxiv.2408.13687

Quantum error correction provides a path to reach practical quantum computing by combining multiple physical qubits into a logical qubit, where the logical error rate is suppressed exponentially as more qubits are added. However, this exponential suppression only occurs if the physical error rate is below a critical threshold. In this work, we present two surface code memories operating below this threshold: a distance-7 code and a distance-5 code integrated with a real-time decoder. The logical error rate of our larger quantum memory is suppressed by a factor of $\Lambda$ = 2.14 $\pm$ 0.02 when increasing the code distance by two, culminating in a 101-qubit distance-7 code with 0.143% $\pm$ 0.003% error per cycle of error correction. This logical memory is also beyond break-even, exceeding its best physical qubit's lifetime by a factor of 2.4 $\pm$ 0.3. We maintain below-threshold performance when decoding in real time, achieving an average decoder latency of 63 $\mu$s at distance-5 up to a million cycles, with a cycle time of 1.1 $\mu$s. To probe the limits of our error-correction performance, we run repetition codes up to distance-29 and find that logical performance is limited by rare correlated error events occurring approximately once every hour, or 3 $\times$ 10$^9$ cycles. Our results present device performance that, if scaled, could realize the operational requirements of large scale fault-tolerant quantum algorithms.