QSE Quantum Seminar: Towards the experimental implementation of a critical Schrödinger-cat qubit

Please join us for the QSE Center Quantum Seminar with Dr. Alexander Grimm from PSI, who will give the talk "Towards the experimental implementation of a critical Schrödinger-cat qubit" on Thursday April 25.
Location: CM 1 221

Pizzas will be available before the seminar at 12:00. All PhDs, postdocs, students, and PIs are welcome to join us.

TITLE: Towards the experimental implementation of a critical Schrödinger-cat qubit

ABSTRACT: Quantum two-level systems are routinely used to encode qubits but tend to be inherently fragile, leading to errors in the encoded information. Quantum error correction (QEC) addresses this challenge by encoding effective qubits into more complex quantum systems. Unfortunately, the hardware overhead associated with QEC can quickly become very large.
In contrast, a qubit that is intrinsically protected against a subset of quantum errors can be encoded into superpositions of two opposite-phase oscillations in a resonator, so-called Schrödinger-cat states [1]. There are various methods [2,3] to stabilize and manipulate the basis states of such a “Schrödinger-cat qubit” which has the potential to significantly reduce the complexity of QEC. I will describe how these methods can be combined in the so-called “critical” Schrödinger-cat qubit [4] and discuss our progress towards its experimental implementation.

BIO: Alexander is the group leader of the bosonic quantum information group at the Paul Scherrer Institut. He obtained his PhD for research done between 2011 and 2015 in the group of Max Hofheinz at CEA Grenoble. During this time, he experimentally demonstrated that inelastic Cooper pair tunneling through a voltage-biased Josephson junction can be leveraged to create a source of antibunched microwave radiation. From 2016 to 2019 he was part of the group of Michel Devoret at Yale University as a postdoctoral associate, working on autonomous quantum error correction (QEC) in bosonic codes. There, he performed various QEC experiments including the demonstration and operation of a ‘’Kerr-cat qubit’’, a type of bosonic qubit which is encoded into superpositions of stabilized coherent states. For his contributions to the field of quantum information processing with non-linear effects in Josephson junctions he received the 2022 Nicholas Kurti prize. 

References:
[1] Mirrahimi, M. et al. New J. Phys. 16, 045014 (2014).
[2] Leghtas, Z. et al. Science 347, 853–857 (2015).
[3] Grimm, A. , Frattini N.E., et al. Nature 584, 205–209 (2020).
[4] Gravina, L., Minganti, F. & Savona, V. PRX Quantum 4, 020337 (2023).