Episode 146

Quantum rotor codes can encode logical qudits or rotors in the space of multiple quantum rotors. Such rotors can be physically realized by superconducting devices composed of multiple islands, each island given by an integer Cooper pair charge and its conjugate phase. We discuss how, for homological rotor codes, the homology of the underlying chain complex determines what is encoded and show how a tesselation of the real projective plane or a Möbius strip encodes a qubit, a 0-\pi qubit. We discuss the nature of the protection of such 2D rotor codes: due to the phenomenon of logical operator spreading by continuous stabilizer phase-shifts, one expects a limited memory phase. We discuss the protected 0-\pi qubit and Kitaev's Moebius-strip qubit from this code perspective.

Talk is based on Vuillot, Ciani, Terhal, Homological Quantum Rotor Codes: Logical Qubits from Torsion, [ Ссылка ]

Barbara Terhal is a Dutch theorist working in quantum information theory since her PhD in 1999. She was a visitor, then a postdoc and then a research staff member at IBM Watson in Yorktown Heights until 2010, working on topics such as entanglement witnesses, the power of constant-depth circuits, quantum complexity theory and quantum error correction and fault-tolerance. In 2010 she left IBM to become professor in theoretical physics at RWTH Aachen University, and she moved to Delft University of Technology in 2017. She has been a fellow of the American Physical Society since 2007, a distinguished visiting research chair at Perimeter Institute since 2014 and a fellow of the Royal Netherlands Academy of Arts and Sciences since 2020.

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