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A classical obfuscator for quantum circuits is a classical program that, given the classical description of a quantum circuit Q, outputs the classical description of a functionally equivalent quantum circuit Q' that hides as much as possible about Q. Previously, the only known feasibility result for classical obfuscation of quantum circuits (Bartusek and Malavolta, ITCS 2022) was limited to "null" security, which is only meaningful for circuits that always reject. On the other hand, if the obfuscator is allowed to compile the quantum circuit Q into a quantum state |Q'>, there exist feasibility results for obfuscating much more expressive classes of circuits: All pseudo-deterministic quantum circuits (Bartusek, Kitagawa, Nishimaki and Yamakawa, STOC 2023, Bartusek, Brakerski and Vaikuntanathan, STOC 2024), and even all unitaries (Huang and Tang, FOCS 2025).

We show that (relative to a classical oracle) there exists a classical obfuscator for all pseudo-deterministic quantum circuits. As our main technical step, we give the first construction of a compact quantum fully-homomorphic encryption (QFHE) scheme that supports public verification of (pseudo-deterministic) quantum evaluation, relative to a classical oracle.

To construct our QFHE scheme, we improve on an approach introduced by Bartusek, Kitagawa, Nishimaki and Yamakawa (STOC 2023), which previously required ciphertexts that are both quantum and non-compact due to a heavy use of quantum coset states and their publicly-verifiable properties. As part of our core technical contribution, we introduce new techniques for analyzing coset states that can be generated "on the fly", by proving new cryptographic properties of the one-shot signature scheme of Shmueli and Zhandry (CRYPTO 2025). Our techniques allow us to produce QFHE ciphertexts that are purely classical, compact, and publicly-verifiable. This additionally yields the first classical verification of quantum computation protocol for BQP that simultaneously satisfies blindness and public-verifiability. 

This is based on joint work with James Bartusek, Saachi Mutreja and Omri Shmueli.

Program obfuscation asks whether a program can be transformed into a protected form that preserves its behavior while hiding the details of its implementation. For quantum computation, achieving such a guarantee for general quantum circuits has long been a major challenge, with prior progress limited to special classes of quantum programs.

In this talk, I will present new constructions that move beyond restricted quantum programs toward fully general quantum computation. I first give an obfuscation scheme for unitary quantum programs with quantum inputs and outputs, going beyond previous pseudo-deterministic settings. Building on this result, and combined with the subspace-preserving pseudorandom unitaries we introduce, we obtain a quantum ideal obfuscation scheme for arbitrary quantum circuits computing general completely positive trace-preserving (CPTP) maps. The constructions are proven secure assuming post-quantum one-way functions in the classical oracle model.