From qmeso at itp.ac.ru  Tue Dec  7 16:55:35 2021
From: qmeso at itp.ac.ru (Quantum Mesoscopics Dept.)
Date: Tue, 07 Dec 2021 16:55:35 +0300
Subject: [qmeso-seminar] =?utf-8?b?0YHQtdC80LjQvdCw0YAgMTAg0LTQtdC60LA=?=
 =?utf-8?b?0LHRgNGP?=
Message-ID: <mailman.0.1638885355.4018138.qmeso-seminar@itp.ac.ru>


СЕМИНАР СЕКТОРА КВАНТОВОЙ МЕЗОСКОПИКИ

пятница 10 декабря, 16:00, онлайн


Claudio Chamon (Boston University, USA)

Superconducting Circuit Realization of Combinatorial Gauge Symmetry


We propose a superconducting quantum circuit based on a general symmetry principle—combinatorial gauge symmetry—designed to emulate topologically ordered quantum liquids and serve as a foundation for the construction of topological qubits. The proposed circuit exhibits rich features: in the classical limit of large capacitances its ground state consists of two superimposed loop structures; one is a crystal of small loops containing disordered U(1) degrees of freedom, and the other is a gas of loops of all sizes associated with Z2 topological order. We show that these classical results carry over to the quantum case, where phase fluctuations arise from the presence of finite capacitances, yielding Z2 quantum topological order. A key feature of the exact gauge symmetry is that amplitudes connecting different Z2 loop states arise from paths having zero classical energy cost. As a result, these amplitudes are controlled by dimensional confinement rather than tunneling through energy 
 barriers. We argue that this effect may lead to larger energy gaps than previous proposals that are limited by such barriers, potentially making it more likely for a topological phase to be experimentally observable. Finally, we discuss how our superconducting circuit realization of combinatorial gauge symmetry can be implemented in practice.

<a href="https://doi.org/10.1103/PRXQuantum.2.030341">PRX QUANTUM 2, 030341 (2021)</a>

(<font color="#ff0000"><b>Необычное время: 16.00!</b></font> Трансляция: <a
href="https://zoom.us/j/96948399564?pwd=RXlKbW96Qm1tZEV6SHB0Q2JYeTdrdz09">Zoom</a>)

подробнее: http://qmeso.itp.ac.ru/seminars.php?abstract=true


From qmeso at itp.ac.ru  Tue Dec 14 11:45:56 2021
From: qmeso at itp.ac.ru (Quantum Mesoscopics Dept.)
Date: Tue, 14 Dec 2021 11:45:56 +0300
Subject: [qmeso-seminar] =?utf-8?b?0YHQtdC80LjQvdCw0YAgMTcg0LTQtdC60LA=?=
 =?utf-8?b?0LHRgNGP?=
Message-ID: <mailman.0.1639471574.835015.qmeso-seminar@itp.ac.ru>


СЕМИНАР СЕКТОРА КВАНТОВОЙ МЕЗОСКОПИКИ

пятница 17 декабря, 15:00, ИТФ


_Aleksey V. Lunkin_ and Mikhail V. Feigel'man

High-frequency transport and zero-sound in an array of SYK quantum dots


We study an array of strongly correlated quantum dots of complex SYK type and account for the effects of quadratic terms added to the SYK Hamiltonian; both local terms and inter-dot tunneling are considered in the non-Fermi-liquid temperature range T >> T_FL Electric σ(ω, p) and thermal κ(ω, p) conductivities are calculated as functions of frequency and momentum, for arbitrary values of the particle-hole asymmetry parameter. At low frequencies ω << T we find the Lorentz ratio L = κ(0, 0)/σ(0, 0) to be non-universal and temperature-dependent. At ω >> T the conductivity σ(ω, p) contains a pole with nearly linear dispersion ω ≈ sp ln (ω/T) reminiscent of the "zero-sound", known for Fermi-liquids.

[Трансляция: https://zoom.us/j/96948399564?pwd=RXlKbW96Qm1tZEV6SHB0Q2JYeTdrdz09]

подробнее: http://qmeso.itp.ac.ru/seminars.php?abstract=true