Real-Valued Somewhat-Pseudorandom Unitaries

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Hauptverfasser: Brakerski, Zvika, Magrafta, Nir
Format: Preprint
Veröffentlicht: 2024
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author Brakerski, Zvika
Magrafta, Nir
author_facet Brakerski, Zvika
Magrafta, Nir
contents We explore a very simple distribution of unitaries: random (binary) phase -- Hadamard -- random (binary) phase -- random computational-basis permutation. We show that this distribution is statistically indistinguishable from random Haar unitaries for any polynomial set of orthogonal input states (in any basis) with polynomial multiplicity. This shows that even though real-valued unitaries cannot be completely pseudorandom (Haug, Bharti, Koh, arXiv:2306.11677), we can still obtain some pseudorandom properties without giving up on the simplicity of a real-valued unitary. Our analysis shows that an even simpler construction: applying a random (binary) phase followed by a random computational-basis permutation, would suffice, assuming that the input is orthogonal and \emph{flat} (that is, has high min-entropy when measured in the computational basis). Using quantum-secure one-way functions (which imply quantum-secure pseudorandom functions and permutations), we obtain an efficient cryptographic instantiation of the above.
format Preprint
id arxiv_https___arxiv_org_abs_2403_16704
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Real-Valued Somewhat-Pseudorandom Unitaries
Brakerski, Zvika
Magrafta, Nir
Quantum Physics
Cryptography and Security
We explore a very simple distribution of unitaries: random (binary) phase -- Hadamard -- random (binary) phase -- random computational-basis permutation. We show that this distribution is statistically indistinguishable from random Haar unitaries for any polynomial set of orthogonal input states (in any basis) with polynomial multiplicity. This shows that even though real-valued unitaries cannot be completely pseudorandom (Haug, Bharti, Koh, arXiv:2306.11677), we can still obtain some pseudorandom properties without giving up on the simplicity of a real-valued unitary. Our analysis shows that an even simpler construction: applying a random (binary) phase followed by a random computational-basis permutation, would suffice, assuming that the input is orthogonal and \emph{flat} (that is, has high min-entropy when measured in the computational basis). Using quantum-secure one-way functions (which imply quantum-secure pseudorandom functions and permutations), we obtain an efficient cryptographic instantiation of the above.
title Real-Valued Somewhat-Pseudorandom Unitaries
topic Quantum Physics
Cryptography and Security
url https://arxiv.org/abs/2403.16704