QUASAR weekly seminar talk.

• Date: Tuesday, November 18, 2025
• Time: 10:30-11:30 AM ET
• Location: STEM Complex
• Speaker: Alper Cakan
• Affiliation: Carnegie Mellon University

Abstract

Quantum fire is a distribution of quantum states that can be efficiently cloned, but cannot be efficiently converted into a classical string. Introduced by Nehoran and Zhandry (ITCS’24) and formalized by Bostanci, Nehoran, Zhandry (STOC’25), quantum fire has various applications in cryptography, along with important implications to physics and complexity. However, constructing and proving security of quantum fire so far has been elusive. Nehoran and Zhandry showed how to construct quantum fire relative to an inefficient quantum oracle (which cannot be instantiated even heuristically). Later, Bostanci, Nehoran, Zhandry gave a candidate construction based on group actions; however, even in the classical oracle model they could only conjecture the security of their scheme, and were not able to give a security proof or argue security.

In this work, for the first time we give a construction of public-key quantum fire relative to a classical oracle and prove its security unconditionally. This also gives the first (classical oracle) separation between the two fundamental principles of quantum mechanics in a computational world that are equivalent in the information-theoretic setting: no-cloning and no-teleportation.

Going further, we also introduce two stronger notions that generalize quantum fire, and we give secure constructions for these primitives.

• We introduce a notion called quantum key-fire where the clonable fire states encode a functionality (such as a signing or decryption key) and can be used to evaluate this functionality, and for security we require that given the fire state, the functionality cannot be efficiently encoded into a classical string.
• We consider the notion of interactive security, where instead of trying to encode the functionality into a classical string, the adversary, given the flame state, attempts to transfer the functionality to another adversary interactively over a classical channel. We call this security notion LOCC leakage-resilience.

We give a construction of quantum key-fire relative to a classical oracle and unconditionally prove that it satisfies LOCC leakage-resilience for any (unlearnable) functionality. In all of our constructions, the oracles can be implemented efficiently using one-way functions. Thus, when our scheme is instantiated with one-way functions and indistinguishability obfuscation, our work also gives the first construction in the plain model that is heuristically secure.