Overcoming leakage in scalable quantum error correction
Creators: name: Miao, Kevin C.
name: McEwen, Matt
name: Atalaya, Juan
name: Kafri, Dvir
name: Pryadko, Leonid P.
name: Bengtsson, Andreas
name: Opremcak, Alex
name: Satzinger, Kevin J.
name: Chen, Zijun
name: Klimov, Paul V.
name: Quintana, Chris
name: Acharya, Rajeev
name: Anderson, Kyle
name: Ansmann, Markus
name: Arute, Frank
name: Arya, Kunal
name: Asfaw, Abraham
name: Bardin, Joseph C.
name: Bourassa, Alexandre
name: Bovaird, Jenna
name: Brill, Leon
name: Buckley, Bob B.
name: Buell, David A.
name: Burger, Tim
name: Burkett, Brian
name: Bushnell, Nicholas
name: Campero, Juan
name: Chiaro, Ben
name: Collins, Roberto
name: Conner, Paul
name: Crook, Alexander L.
name: Curtin, Ben
name: Debroy, Dripto M.
name: Demura, Sean
name: Dunsworth, Andrew
name: Erickson, Catherine
name: Fatemi, Reza
name: Ferreira, Vinicius S.
name: Burgos, Leslie Flores
name: Forati, Ebrahim
name: Fowler, Austin G.
name: Foxen, Brooks
name: Garcia, Gonzalo
name: Giang, William
name: Gidney, Craig
name: Giustina, Marissa
name: Gosula, Raja
name: Dau, Alejandro Grajales
name: Gross, Jonathan A.
name: Hamilton, Michael C.
name: Harrington, Sean D.
name: Heu, Paula
name: Hilton, Jeremy
name: Hoffmann, Markus R.
name: Hong, Sabrina
name: Huang, Trent
name: Huff, Ashley
name: Iveland, Justin
name: Jeffrey, Evan
name: Jiang, Zhang
name: Jones, Cody
name: Kelly, Julian
name: Kim, Seon
name: Kostritsa, Fedor
name: Kreikebaum, John Mark
name: Landhuis, David
name: Laptev, Pavel
name: Laws, Lily
name: Lee, Kenny
name: Lester, Brian J.
name: Lill, Alexander T.
name: Liu, Wayne
name: Locharla, Aditya
name: Lucero, Erik
name: Martin, Steven
name: Megrant, Anthony
name: Mi, Xiao
name: Montazeri, Shirin
name: Morvan, Alexis
name: Naaman, Ofer
name: Neeley, Matthew
name: Neill, Charles
name: Nersisyan, Ani
name: Newman, Michael
name: Ng, Jiun How
name: Nguyen, Anthony
name: Nguyen, Murray
name: Potter, Rebecca
name: Rocque, Charles
name: Roushan, Pedram
name: Sankaragomathi, Kannan
name: Schuster, Christopher
name: Shearn, Michael J.
name: Shorter, Aaron
name: Shutty, Noah
name: Shvarts, Vladimir
name: Skruzny, Jindra
name: Smith, W. Clarke
name: Sterling, George
name: Szalay, Marco
name: Thor, Douglas
name: Torres, Alfredo
name: White, Theodore
name: Woo, Bryan W. K.
name: Yao, Z. Jamie
name: Yeh, Ping
name: Yoo, Juhwan
name: Young, Grayson
name: Zalcman, Adam
name: Zhu, Ningfeng
name: Zobrist, Nicholas
name: Neven, Hartmut
name: Smelyanskiy, Vadim
name: Petukhov, Andre
name: Korotkov, Alexander N.
name: Sank, Daniel
name: Chen, Yu
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Leakage of quantum information out of computational states into higher energy states represents a major challenge in the pursuit of quantum error correction (QEC). In a QEC circuit, leakage builds over time and spreads through multi-qubit interactions. This leads to correlated errors that degrade the exponential suppression of logical error with scale, challenging the feasibility of QEC as a path towards fault-tolerant quantum computation. Here, we demonstrate the execution of a distance-3 surface code and distance-21 bit-flip code on a Sycamore quantum processor where leakage is removed from all qubits in each cycle. This shortens the lifetime of leakage and curtails its ability to spread and induce correlated errors. We report a ten-fold reduction in steady-state leakage population on the data qubits encoding the logical state and an average leakage population of less than $1 \times 10^{-3}$ throughout the entire device. The leakage removal process itself efficiently returns leakage population back to the computational basis, and adding it to a code circuit prevents leakage from inducing correlated error across cycles, restoring a fundamental assumption of QEC. With this demonstration that leakage can be contained, we resolve a key challenge for practical QEC at scale.
description: Main text: 7 pages, 5 figures