Decentralized Consensus from Quantum Proof of Position

We construct an energy efficient consensus protocol with geospatial position as an external resource by using quantum computers. Economic resources of some form are essential in decentralized consensus protocols in order to prevent attacks in which malicious parties costlessly generate fake identities. The resulting protocol, Quantum Proof of Position (QPoP), improves on existing classical mechanisms: it dispenses with the notorious electricity consumption of Proof-of-Work, and, because its resource is external to the protocol, with the wealth concentration of Proof-of-Stake. QPoP also has two properties that, to our knowledge, no other permissionless Sybil resistance mechanism possesses. First, its Sybil resistance is non-rival: position verification occupies a quantum computer only briefly, so a single device can secure any number of chains at once, each enjoying its full benefit. Second, the protocol generates geographic decentralization, because its resource cannot be agglomerated: a participant's power is the number of distinct locations at which it operates a quantum computer, and a second computer at an occupied location adds nothing.