Yasuhiro Utsumi’s scientific contributions

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Publications (2)

FIG. 5. Geometric current J g and its bounds as functions of the frequency ω = 2π/T 0 . We set k(t ) = k as a constant, r(t ) = 0.2 × [sin(ωt ) + cos(ωt )], and k (R) (t )/k = 0.5 × (1 + 0.8 × sin(ωt − 0.6π )). The red line (bound 1) denotes the bound (60) with Eq. (58) and the blue line (bound 2) denotes that with Eq. (59). We also show the trivial bound |J g | 1 T 0
Generalized speed limits for classical stochastic systems and their applications to relaxation, annealing, and pumping processes
  • Article
  • Full-text available

March 2023

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9 Reads

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3 Citations

Physical Review Research

Kazutaka Takahashi

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Yasuhiro Utsumi

We extend the speed limit of a distance between two states evolving by different generators for quantum systems [K. Suzuki and K. Takahashi, Phys. Rev. Res. 2, 032016(R) (2020)] to the classical stochastic processes described by the master equation. We demonstrate that the trace distance between arbitrary evolving states is bounded from above by using a geometrical metric. The geometrical bound reduces to the Fisher information metric for the distance between the time-evolved state and the initial state. We compare the bound in relaxation and annealing processes with a different type of bound known for nonequilibrium thermodynamical systems. For dynamical processes such as annealing and pumping processes, the distance between the time-evolved state and the instantaneous stationary state becomes a proper choice and the bound is represented by the Fisher information metric of the stationary state. The metric is related to the counterdiabatic term defined from the time dependence of the stationary state.

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FIG. 4. Annealing processes for three-state systems. We adopt the energy levels and the protocols used in Fig. 1. The lower thick solid line (blue) represents Eq. (39) and the upper thick solid line (red) represents Eq. (41). The bounds in the right panel are larger than p st 1 (t) − p st 1 (0) depicted by the dashed line (blue). The thin solid lines (black) are plotted by solving the master equation numerically with the transitionrate matrix in Eq. (43). We generate random numbers for parameters a, b, c, and δ(t) to plot 40 samples in each panel. We set at f , bt f , ct f ≤ 10 and δ(t) is chosen so that |δ(t)| ≤ min(a/π3, b/π2, c/π1) is satisfied.
FIG. 5. Geometric current Jg and its bounds as functions of the frequency ω = 2π/T0. We set that k(t) = k is a constant, r(t) = 0.2 × [sin(ωt) + cos(ωt)], and k (R) (t)/k = 0.5 × (1 + 0.8 × sin(ωt − 0.6π)). The red line (bound 1) denotes the bound (60) with Eq. (58) and the blue line (bound 2) denotes that with Eq. (59). We also show the trivial bound |Jg| ≤ 1 T 0
Generalized speed limits for classical stochastic systems and their applications to relaxation, annealing, and pumping processes

August 2022

·

24 Reads

Kazutaka Takahashi

·

Yasuhiro Utsumi

We extend the speed limit of a distance between two states evolving by different generators for quantum systems [K. Suzuki and K. Takahashi, Phys. Rev. Res. 2, 032016(R) (2020)] to the classical stochastic processes described by the master equation. We demonstrate that the trace distance between arbitrary evolving states is bounded from above by using a geometrical metric. The geometrical bound reduces to the Fisher information metric for the distance between the time-evolved state and the initial state. We compare the bound in relaxation and annealing processes with a different type of bound known for nonequilibrium thermodynamical systems. For dynamical processes such as annealing and pumping processes, the distance between the time-evolved state and the instantaneous stationary state becomes a proper choice and the bound is represented by the Fisher information metric of the stationary state. The metric is related to the counterdiabatic term defined from the time dependence of the stationary state.

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Citations (1)

... Our QD circuit is designed for information processing, and its operation speed necessitates a novel performance measure. We focus on the particle emission rate as such a measure and demonstrate that it is well estimated using the thermodynamic speed limit relation [12,14,25] applied to a subsystem within bipartite dynamics. ...

Reference:

Conservative Join with memory in token-based Brownian circuits and its thermodynamic cost
Generalized speed limits for classical stochastic systems and their applications to relaxation, annealing, and pumping processes

Physical Review Research

Kazutaka Takahashi

·

Yasuhiro Utsumi