22 citations · 146 across the 26 of their papers we have counts for
23 papers · 1 filter
Universal tradeoff relations between resource cost and irreversibility of channels: General-resource Wigner-Araki-Yanase theorems and beyond
Hiroyasu Tajima, Koji Yamaguchi, Ryuji Takagi +1
Quantum technologies offer exceptional -- sometimes almost magical -- speed and performance, yet every quantum process costs physical resources. Designing next-generation quantum d…
Asymptotically tight security analysis of quantum key distribution based on universal source compression
Takaya Matsuura, Shinichiro Yamano, Yui Kuramochi +2
Practical quantum key distribution (QKD) protocols require a finite-size security proof. The phase error correction (PEC) approach is one of the general strategies for security ana…
Nonstandard derivation of the Gorini-Kossakowski-Sudarshan-Lindblad master equation of a quantum dynamical semigroup from the Kraus representation
Yui Kuramochi
We give a new nonstandard proof of the well-known theorem that the generator of a quantum dynamical semigroup on a finite-dimensional quantum system has a specific f…
Tight concentration inequalities for quantum adversarial setups exploiting permutation symmetry
Takaya Matsuura, Shinichiro Yamano, Yui Kuramochi +2
We developed new concentration inequalities for a quantum state on an -qudit system or measurement outcomes on it that apply to an adversarial setup, where an adversary prepares…
Standard quantum limit of finite-size optical lattice clock in estimating gravitational potential
Fumiya Nishimura, Yui Kuramochi, Kazuhiro Yamamoto
We evaluated the accuracy limit for estimating gravitational potential using optical lattice clocks by utilizing the quantum Cramér--Rao bound. We then compared the results for sin…
General treatment of Gaussian trusted noise in continuous variable quantum key distribution
Shinichiro Yamano, Takaya Matsuura, Yui Kuramochi +2
Continuous Variable (CV) quantum key distribution (QKD) is a promising candidate for practical implementations due to its compatibility with the existing communication technology.…
Refined finite-size analysis of binary-modulation continuous-variable quantum key distribution
Takaya Matsuura, Shinichiro Yamano, Yui Kuramochi +2
Recent studies showed the finite-size security of binary-modulation CV-QKD protocols against general attacks. However, they gave poor key-rate scaling against transmission distance…
Finite-size security proof of binary-modulation continuous-variable quantum key distribution using only heterodyne measurement
Shinichiro Yamano, Takaya Matsuura, Yui Kuramochi +2
Continuous-variable quantum key distribution (CV-QKD) has many practical advantages including compatibility with current optical communication technology. Implementation using hete…
Wigner-Araki-Yanase theorem for continuous and unbounded conserved observables
Yui Kuramochi, Hiroyasu Tajima
The Wigner-Araki-Yanase (WAY) theorem states that additive conservation laws imply the commutativity of exactly implementable projective measurements and the conserved observables…
Universal trade-off structure between symmetry, irreversibility, and quantum coherence in quantum processes
Hiroyasu Tajima, Ryuji Takagi, Yui Kuramochi
Symmetry, irreversibility, and quantum coherence are foundational concepts in physics. Here, we present a universal tradeoff relation between these three concepts. This particularl…
Infinite dimensionality of the post-processing order of measurements on a general state space
Yui Kuramochi
For a partially ordered set , the order (monotone) dimension is the minimum cardinality of total orders (respectively, real-valued order monotone functions) o…
Post-processing minimal joint observables
Teiko Heinosaari, Yui Kuramochi
A finite set of quantum observables (positive operator valued measures) is called compatible if these observables are marginals of a some observable, called a joint observable of t…
Entanglement-breaking channels with general outcome operator algebras
Yui Kuramochi
A unit-preserving and completely positive linear map, or a channel, between -algebras and $\mathcal{A}_{\m…
Directed-completeness of quantum statistical experiments in the randomization order
Yui Kuramochi
A parametrized family of normal states on a von Neumann algebra is called a statistical experiment, which generalizes the corresponding concepts in classical statistics and finite-…
Accessible information without disturbing partially known quantum states on a von Neumann algebra
Yui Kuramochi
This paper addresses the problem of how much information we can extract without disturbing a statistical experiment, which is a family of partially known normal states on a von Neu…
Quantum incompatibility of channels with general outcome operator algebras
Yui Kuramochi
A pair of quantum channels are said to be incompatible if they cannot be realized as marginals of a single channel. This paper addresses the general structure of the incompatibilit…
Minimal sufficient statistical experiments on von Neumann algebras
Yui Kuramochi
A statistical experiment on a von Neumann algebra is a parametrized family of normal states on the algebra. This paper introduces the concept of minimal sufficiency for statistical…
Saturation of repeated quantum measurements
Erkka Haapasalo, Teiko Heinosaari, Yui Kuramochi
We study sequential measurement scenarios where the system is repeatedly subjected to the same measurement process. We first provide examples of such repeated measurements where fu…
Minimal sufficient positive-operator valued measure on a separable Hilbert space
Yui Kuramochi
We introduce a concept of a minimal sufficient positive-operator valued measure (POVM), which is the least redundant POVM among the POVMs that have the equivalent information about…
Tradeoff Relation between Information and Disturbance in Quantum Measurement
Tomohiro Shitara, Yui Kuramochi, Masahito Ueda
When we extract information from a system by performing a quantum measurement, the state of the system is disturbed due to the backaction of the measurement. Numerous studies have…
Construction of the least informative observable conserved by a given quantum instrument
Yui Kuramochi
For a quantum measurement process described by a quantum instrument and a system observable corresponding to a positive-operator valued measure (POVM) $\mathcal…
Classicality condition on a system's observable in a quantum measurement and relative-entropy conservation law
Yui Kuramochi, Masahito Ueda
We consider the information flow on a system's observable corresponding to a positive-operator valued measure under a quantum measurement process described by a completely…
Simultaneous continuous measurement of photon-counting and homodyne detection on a free photon field: dynamics of state reduction and mutual influence of measurement backaction
Yui Kuramochi, Yu Watanabe, Masahito Ueda
We analyze a simultaneous continuous measurement of photon-counting and homodyne detection. The stochastic master equation or stochastic Schrödinger equation describing the measure…