Loss-tolerant quantum secure positioning with weak laser sources

Abstract

Quantum position verification (QPV) is the art of verifying the geographical location of an untrusted party. Recently, it has been shown that the widely studied Bennett & Brassard 1984 (BB84) QPV protocol is insecure after the 3 dB loss point assuming local operations and classical communication (LOCC) adversaries. Here, we propose a time-reversed entanglement swapping QPV protocol (based on measurement-device-independent quantum cryptography) that is highly robust against quantum channel loss. First, assuming ideal qubit sources, we show that the protocol is secure against LOCC adversaries for any quantum channel loss, thereby overcoming the 3 dB loss limit. Then, we analyze the security of the protocol in a more practical setting involving weak laser sources and linear optics. In this setting, we find that the security only degrades by an additive constant and the protocol is able to verify positions up to 47 dB channel loss.

Practically secure quantum position verification

“…This is a scheme making use of entanglement of two qubits received by the prover, and is secure if the adversaries share no EPR pairs [19].…”

“…We allow each party to have access to the classical random oracle (19). The steps of this protocol are as follows:…”

“…As it turns out, all of these proposed schemes can be broken by colluding adversaries employing teleportation-based attacks [5,7,12,13]. Various other QPV protocols and attack strategies by adversaries have been proposed [13][14][15][16][17][18][19][20] along with a security analysis with different physical constraints on the colluding adversaries, among which Ref. [15] was the first to make use of random oracle in the protocol.…”