Theory Seminar: Parity Measurements in Action: Detecting Errors in the Surface Code and Heralding Itinerant Cat States using Superconducting Circuits.

Christopher Eichler (ETH Zurich)
Parity measurements distinguish between quantum states with an even and an odd number of excitations without revealing any additional information about the state.

Christopher Eichler (ETH Zurich)
Herbert-Walther Lecture Hall G0.25
Wed, 5. February 2020, 11:30 am

Abstract:

Parity measurements distinguish between quantum states with an even and an odd number of excitations without revealing any additional information about the state. Nondestructive parity detection allows one to project onto highly entangled states and therefore plays a central role in quantum error correction. In my talk, I discuss two complementary implementations of parity detection both realized in superconducting circuits. First, we measure the parity of the photon number of propagating radiation fields and thereby herald itinerant Schrödinger cat states [1]. Second, we perform ancilla-based parity detection in multi-qubit systems to implement the smallest viable instance of the surface code capable of detecting any single error [2]. Both experiments crucially rely on recent progress in performing high-fidelity, fast, and qubit-selective readout [3], and highlight the great potential of superconducting circuits for quantum information science.

[1] J. - C. Besse, S. Gasparinetti, M. C. Collodo, T. Walter, A. Remm, J. Krause, C. Eichler, and A. Wallraff, arXiv:1912.09896 (2019); J. - C. Besse, S. Gasparinetti, M. C. Collodo, T. Walter, P. Kurpiers, M. Pechal, C. Eichler, and A. Wallraff, Phys. Rev. X 8, 021003 (2018) [2] C. Kraglund Andersen, A. Remm, S. Lazar, S. Krinner, N. Lacroix, G. J. Norris, M. Gabureac, C. Eichler, and A. Wallraff, arXiv:1912.09410 (2019); C. Kraglund Andersen*, A. Remm*, S. Lazar, S. Krinner, J. Heinsoo, J-C. Besse, M. Gabureac, A. Wallraff, and C. Eichler, NPJ Quantum Information 5, 69 (2019) [3] J. Heinsoo, C. Kraglund Andersen, A. Remm, S. Krinner, T. Walter, Y. Salathe, S. Gasparinetti, J-C. Besse, A. Potocnik, A. Wallraff, and C. Eichler, Phys. Rev. Applied 10, 034040 (2018); T. Walter, P. Kurpiers, S. Gasparinetti, P. Magnard, A. Potoćnik, Y. Salathe, M. Pechal, M. Mondal, M. Oppliger, C. Eichler, and A. Wallraff, Phys. Rev. Applied 7, 054020 (2017)