Abstract:
Public-key Quantum Token Schemes are executed in a system of quantum computers, and allow a sender holding a quantum computer to sample a quantum state which is unclonable (to everyone in the system), but also publicly verifiable. Such schemes imply powerful primitives like public-key quantum money, give a technical basis for tasks like provable software copy-protection and are at the heart of quantum cryptography.
While quantum token schemes allow to realize high-end tasks, their main drawback is that they require a strong computational model to be implemented - quantum computation and a quantum communication infrastructure.

A central open question in the field was whether we can have a stronger primitive, called a (Public-key) Semi-quantum Token Scheme, that achieves the same functionality, relying only on local quantum computation and classical communication. The question regarding the existence of such schemes (first defined as Semi-quantum Money) was first posed by Radian and Sattath (AFT 2019), and since, no construction was known under any computational assumption.

In this talk we introduce public-key quantum token schemes, review their short history and show our solution on how to construct a public-key semi-quantum token scheme using computational assumptions.