Universal channel coding enables communication without a complete description of the channel. For classical channels, universal codes can attain both capacity and the optimal high-rate reliability. We show that this compatibility fails for classical-quantum channels in general; that is, the optimal reliability in the c...
Kaito Watanabe, Masahito Hayashi, Takaya Matsuura et al.· 0 citations
The generalised quantum Stein's lemma is a key result in quantum hypothesis testing, and connects this fundamental primitive of quantum information processing with quantum resource manipulation, a task that is central for technological applications. Prior works have proved this statement in the idealised setting of ind...
Filippo Girardi, Kuan-Yi Lee, Masahito Hayashi et al.· 3 citations
This work constructs finite-block preprocessing schemes whose private information is an entropy difference evaluated at two distributions related by group convolution, and proves nonadditivity at an explicit channel parameter using a two-use encoder, an analytic single-use converse, and certified entropy bounds.
We present a full-oscillator analysis of a finite-energy GKP CHSH test whose observed score yields robust Bell-pair self-testing. Periodically binned position and momentum give the Pauli settings, while a fixed binary coarse-graining of photon number modulo four and its displaced conjugate realize the tilted settings....
Farzin Salek, Masahito Hayashi· 2 citations
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