Proof-of-work consensus by quantum sampling

TL;DR

This paper introduces a quantum Proof-of-Work scheme using coarse-grained boson sampling, leveraging quantum advantage for blockchain security and efficiency, with incentives for honest participation and robustness against classical spoofing.

Contribution

It proposes a novel quantum PoW protocol based on boson sampling, combining quantum sampling with blockchain consensus and incentive mechanisms.

Findings

Validation tests are hard to spoof classically.

The protocol is robust to photon partial distinguishability.

Provides significant speedup and energy savings over classical computation.

Abstract

Since its advent in 2011, boson sampling has been a preferred candidate for demonstrating quantum advantage because of its simplicity and near-term requirements compared to other quantum algorithms. We propose to use a variant, called coarse-grained boson-sampling (CGBS), as a quantum Proof-of-Work (PoW) scheme for blockchain consensus. The users perform boson sampling using input states that depend on the current block information and commit their samples to the network. Afterwards, CGBS strategies are determined which can be used to both validate samples and reward successful miners. By combining rewards for miners committing honest samples together with penalties for miners committing dishonest samples, a Nash equilibrium is found that incentivizes honest nodes. We provide numerical evidence that these validation tests are hard to spoof classically without knowing the binning scheme ahead of time and show the robustness of our protocol to small partial distinguishability of photons. The scheme works for both Fock state boson sampling and Gaussian boson sampling and provides dramatic speedup and energy savings relative to computation by classical hardware.