9 papers
Structural -divergence: Tight universal bounds for cost function moments and gradients in parameterized quantum circuits
Tomohiro Nishiyama, Yoshihiko Hasegawa
The barren plateau phenomenon, in which cost-function gradients of variational quantum algorithms vanish exponentially, remains a central obstacle for near-term quantum computing.…
Unified speed limits in classical and quantum dynamics via temporal Fisher information
Tomohiro Nishiyama, Yoshihiko Hasegawa
The importance of Fisher information is increasing in nonequilibrium thermodynamics, as it has played a fundamental role in trade-off relations such as thermodynamic uncertainty re…
Unified entropy production in finite quantum systems
Tomohiro Nishiyama, Yoshihiko Hasegawa
In finite-dimensional quantum systems, temperature cannot be uniquely defined. This, in turn, implies that there are several ways to define entropy production in finite-dimensional…
Thermodynamic entropic uncertainty relation
Yoshihiko Hasegawa, Tomohiro Nishiyama
Thermodynamic uncertainty relations reveal a fundamental trade-off between the precision of a trajectory observable and entropy production, where the uncertainty of the observable…
Quantum thermodynamic uncertainty relations without quantum corrections: A coherent-incoherent correspondence approach
Tomohiro Nishiyama, Yoshihiko Hasegawa
We introduce the coherent-incoherent correspondence as a framework for deriving quantum thermodynamic uncertainty relations under continuous measurement in Lindblad dynamics. The c…
A unified framework of unitarily residual measures for quantifying dissipation
Tomohiro Nishiyama, Yoshihiko Hasegawa
Open quantum systems are governed by both unitary and non-unitary dynamics, with dissipation arising from the latter. Traditional quantum divergence measures, such as quantum relat…