Abstract
We propose a conceptual design for a quantum blockchain. Our method involves encoding the blockchain into a temporal GHZ (Greenberger–Horne–Zeilinger) state of photons that do not simultaneously coexist. It is shown that the entanglement in time, as opposed to an entanglement in space, provides the crucial quantum advantage. All the subcomponents of this system have already been shown to be experimentally realized. Furthermore, our encoding procedure can be interpreted as nonclassically influencing the past.
Highlights
Entanglement is an intrinsically quantum effect that involves nonclassical correlations, usually between spatially separated quantum systems [1]
We show that entanglement in time, as opposed to entanglement in space, plays the pivotal role for the quantum benefit over a classical blockchain
The quantum advantage is that the sensitivity towards tampering is significantly amplified, meaning that the full local copy of the blockchain is destroyed if one tampers with a single block; on a classical blockchain, only the blocks after the tampered block are destroyed, which leaves it open to vulnerabilities
Summary
Entanglement is an intrinsically quantum effect that involves nonclassical correlations, usually between spatially separated quantum systems [1]. This phenomenon was described by Einstein as “spooky action at a distance”, and yet it forms the basis of most quantum information platforms, such as quantum computers and quantum networks. Quantum networks distribute quantum information between any two nodes on the network [2,3]. This allows the distributed system to carry out valuable tasks such as quantum key distribution (QKD), which guarantees secure communication through the laws of physics [4,5]. A notable result [8,9]
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