Obfuscation of Unitary Quantum Programs

TL;DR

This paper introduces the first quantum state obfuscation scheme for unitary quantum programs with quantum inputs and outputs, advancing quantum program privacy in the classical oracle model.

Contribution

It presents a novel quantum obfuscation scheme for unitary programs, utilizing a functional quantum authentication scheme and a new compiler for quantum circuits.

Findings

First quantum obfuscation scheme for unitary programs

Supports quantum inputs and outputs in the classical oracle model

Uses a novel quantum authentication and circuit representation method

Abstract

Program obfuscation aims to hide the inner workings of a program while preserving its functionality. In the quantum setting, recent works have obtained obfuscation schemes for specialized classes of quantum circuits. For instance, Bartusek, Brakerski, and Vaikuntanathan (STOC 2024) constructed a quantum state obfuscation scheme, which supports the obfuscation of quantum programs represented as quantum states for pseudo-deterministic quantum programs with classical inputs and outputs in the classical oracle model. In this work, we improve upon existing results by constructing the first quantum state obfuscation scheme for unitary (or approximately unitary) quantum programs supporting quantum inputs and outputs in the classical oracle model. At the core of our obfuscation scheme are two novel ingredients: a functional quantum authentication scheme that allows key holders to learn specific functions of the authenticated quantum state with simulation-based security, and a compiler that represents an arbitrary quantum circuit as a projective linear-plus-measurement quantum program described by a sequence of non-adaptive Clifford gates interleaved with adaptive and compatible measurements.