Join gate with memory in token-conserving Brownian circuits and the thermodynamic cost

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1. Verfasser: Utsumi, Yasuhiro
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Veröffentlicht: 2025
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author Utsumi, Yasuhiro
author_facet Utsumi, Yasuhiro
contents The token-based Brownian circuit harnesses the Brownian motion of particles for computation. The conservative join (CJoin) is a circuit element that synchronizes two Brownian particles, and its realization using repelling particles, such as magnetic skyrmions or electrons, is key to building the Brownian circuit. Here, a theoretical implementation of the CJoin using a simple quantum dot circuit is proposed, incorporating an internal state-a double quantum dot that functions as a one-bit memory, storing the direction of two-particle transfer. A periodic reset protocol is introduced, allowing the CJoin to emit particles in a specific direction. The stochastic thermodynamics under periodic resets identifies the thermodynamic cost as the work done for resets minus the entropy reduction due to resets, with its lower bound remaining within a few multiples of $k_{\rm B} T$ at temperature $T$. Applying the speed limit relation to a subsystem in bipartite dynamics, the number of emitted particles is shown to be relatively tightly bounded from above by an expression involving the subsystem's irreversible entropy production rate and dynamical activity rate.
format Preprint
id arxiv_https___arxiv_org_abs_2505_12390
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Join gate with memory in token-conserving Brownian circuits and the thermodynamic cost
Utsumi, Yasuhiro
Mesoscale and Nanoscale Physics
Statistical Mechanics
The token-based Brownian circuit harnesses the Brownian motion of particles for computation. The conservative join (CJoin) is a circuit element that synchronizes two Brownian particles, and its realization using repelling particles, such as magnetic skyrmions or electrons, is key to building the Brownian circuit. Here, a theoretical implementation of the CJoin using a simple quantum dot circuit is proposed, incorporating an internal state-a double quantum dot that functions as a one-bit memory, storing the direction of two-particle transfer. A periodic reset protocol is introduced, allowing the CJoin to emit particles in a specific direction. The stochastic thermodynamics under periodic resets identifies the thermodynamic cost as the work done for resets minus the entropy reduction due to resets, with its lower bound remaining within a few multiples of $k_{\rm B} T$ at temperature $T$. Applying the speed limit relation to a subsystem in bipartite dynamics, the number of emitted particles is shown to be relatively tightly bounded from above by an expression involving the subsystem's irreversible entropy production rate and dynamical activity rate.
title Join gate with memory in token-conserving Brownian circuits and the thermodynamic cost
topic Mesoscale and Nanoscale Physics
Statistical Mechanics
url https://arxiv.org/abs/2505.12390