Experimental fault-tolerant code switching

RWTH Publications (RWTH Aachen)

Abstract

Quantum error correction is a crucial tool for mitigating hardware errors in quantum computers by encoding logical information into multiple physical qubits. However, no single error-correcting code allows for an intrinsically fault-tolerant implementation of all the gates needed for universal quantum computing [1-3]. One way to tackle this problem is to switch between two suitable error-correcting codes, while preserving the encoded logical information, which in combination give access to a fault-tolerant universal gate set [4-6]. In this work, we present the first experimental implementation of fault-tolerant code switching between two codes. One is the seven-qubit color code [7], which features fault-tolerant CNOT and $H$ quantum gates, while the other one, the 10-qubit code [8], allows for a fault-tolerant $T$-gate implementation. Together they form a complementary universal gate set. Building on essential code switching building blocks, we construct logical circuits and prepare 12 different logical states which are not accessible natively in a fault-tolerant way within a single code. Finally, we use code switching to entangle two logical qubits employing the full universal gate set in a single logical quantum circuit. Our results experimentally open up a new route towards deterministic control over logical qubits with low auxiliary qubit overhead, not relying on the probabilistic preparation of resource states.

Authors 6

1. Ivan Pogorelov

   Universität Innsbruck

   Affiliation as printed

   Universität Innsbruck , Institut für Experimentalphysik , Innsbruck , Austria

2. Friederike Butt Aachen Institute for Quantum Information

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Institute for Quantum Information , RWTH Aachen University , Aachen , Germany

   Institute for Theoretical Nanoelectronics (PGI-2) , Forschungszentrum Jülich , Jülich , Germany

3. Lukas Postler

   Universität Innsbruck

   Affiliation as printed

   Universität Innsbruck , Institut für Experimentalphysik , Innsbruck , Austria

4. Christian D. Marciniak

   Universität Innsbruck

   Affiliation as printed

   Universität Innsbruck , Institut für Experimentalphysik , Innsbruck , Austria

5. Philipp Schindler

   Universität Innsbruck

   Affiliation as printed

   Universität Innsbruck , Institut für Experimentalphysik , Innsbruck , Austria

6. Thomas Monz

   Universität Innsbruck · Alpine Quantum Technologies (Austria)

   Affiliation as printed

   Also at Alpine Quantum Technologies GmbH , Innsbruck , Aus - tria ;

   Universität Innsbruck , Institut für Experimentalphysik , Innsbruck , Austria