Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2406.20022 · Physical Review A

Impossibility of perfect cheating for single-qubit position verification

Anonymous, Yusuf Alnawakhtha

Published Aug 4, 2026• 0 citations
arXivHTMLPDF

Abstract

In quantum position verification (QPV), a prover certifies her location to a set of verifiers by performing a quantum computation. One of the first QPV protocols was proposed by Kent, Munro, and Spiller in 2011: the prover receives a qubit $Q$ from one direction, receives an orthogonal basis $\{ v, v^\perp \}$ from the opposite direction, then measures $Q$ in $\{ v, v^\perp \}$ and broadcasts the result. Several variants of this protocol have been proposed and analyzed, but the question of whether the original protocol is secure has never been fully resolved. In this work we show that there is no perfect finite-dimensional cheating strategy for the single-qubit measurement protocol. Our proof uses tools from real algebraic geometry.

DOI
10.1103/4pcn-d1yj

Related papers

Practically secure quantum position verification

Siddhartha Das, George Siopsis

Abstract We discuss quantum position verification (QPV) protocols in which the verifiers create and send single-qubit states to the prover. QPV protocols using single-qubit states are known to be insecure against adversaries that share a small number of entangled qubits. We introduce QPV protocols that are practically secure: they only require single-qubit states from each of the verifiers, yet their security is broken if the adversaries sharing an impractically large number of entangled qubits employ teleportation-based attacks. These protocols are a modification of known QPV protocols in which we include a classical random oracle without altering the amount of quantum resources needed by the verifiers. We present a cheating strategy that requires a number of entangled qubits shared among the adversaries that grows exponentially with the size of the classical input of the random oracle.

arXiv:1711.03392•New Journal of Physics•Jun 1, 2021•7 citations

Efficient multi-basis quantum position verification secure against generalized adversaries

Wen Yu Kon, Ignatius William Primaatmaja, Kaushik Chakraborty +1 more

Abstract Quantum position verification (QPV) enables multiple verifiers to certify a prover’s location using quantum communication and physical assumptions. With experimental demonstrations of QPV becoming increasingly feasible, enhancing the practicality and security of QPV protocols is more important than ever. In this work, we make three key contributions toward this goal. First, we introduce a robust QPV protocol in which the verifier’s state preparation is independent of channel loss, improving reliability in real-world conditions. Second, we refine existing security analysis techniques to bolster protocol resilience against experimental imperfections. Third, we identify and address some implicit assumptions present in existing security analyses, providing a framework to eliminate such assumptions. Additionally, as an example of QPV application beyond location verification, we illustrate how QPV can be leveraged for authenticating classical communication in quantum key distribution.

arXiv:2506.03549•npj Quantum Information•Oct 31, 2026•0 citations

Quantum position verification in one shot: parallel repetition of the $f$-BB84 and $f$-routing protocols

Llorenç Escolà-Farràs, Florian Speelman

Quantum position verification (QPV) aims to verify an untrusted prover's location by timing communication with them. To reduce uncertainty, it is desirable for this verification to occur in a single round. However, previous protocols achieving one-round secure QPV had critical drawbacks: attackers pre-sharing an EPR pair per qubit could perfectly break them, and their security depended on quantum information traveling at the speed of light in vacuum, a major experimental challenge in quantum networks. In this work, we prove that a single round of interaction suffices for secure position verification while overcoming these limitations. We show that security for a one-round protocol can rely only on the size of the classical information rather than quantum resources, making implementation more feasible, even with a qubit error tolerance of up to 3.6%, which is experimentally achievable with current technology -- and showing that the timing constraints have to apply only to classical communication. In short, we establish parallel repetition of the $f$-BB84 and $f$-routing QPV protocols. As a consequence of our techniques, we also demonstrate an order-of-magnitude improvement in the error tolerance for the sequential repetition version of these protocols, compared to the previous bounds of Nature Physics 18, 623-626 (2022).

arXiv:2503.09544•Mar 12, 2025•0 citations

Position-based cryptography: Single-qubit protocol secure against multi-qubit attacks.

Andreas Blühm, Matthias Christandl, Florian Speelman

While it is known that unconditionally secure position-based cryptography is impossible both in the classical and the quantum setting, it has been shown that some quantum protocols for position verification are secure against attackers which share a quantum state of bounded dimension. In this work, we consider the security of two protocols for quantum position verification that combine a single qubit with classical strings of total length $2n$: The qubit routing protocol, where the classical information prescribes the qubit's destination, and a variant of the BB84-protocol for position verification, where the classical information prescribes in which basis the qubit should be measured. We show that either protocol is secure for a randomly chosen function if each of the attackers holds at most $n/2 - 5$ qubits. With this, we show for the first time that there exists a quantum position verification protocol where the ratio between the quantum resources an honest prover needs and the quantum resources the attackers need to break the protocol is unbounded. The verifiers need only increase the amount of classical resources to force the attackers to use more quantum resources. Concrete efficient functions for both protocols are also given -- at the expense of a weaker but still unbounded ratio of quantum resources for successful attackers. Finally, we show that both protocols are robust with respect to noise, making them appealing for applications.

•Apr 13, 2021•2 citations

Arbitrarily Loss-Tolerant Quantum Position Verification in a Single Execution

Llorenç Escolà-Farràs, Boris Škorić, Florian Speelman

Quantum position verification (QPV) aims to certify the location of an untrusted prover, but faces two major obstacles: fundamentally, entanglement-based attacks and, experimentally, photon loss. A commitment-based modification introduced in Phys. Rev. Lett. 135, 260801 addresses both in sequentially repeated protocols. Its security analysis, however, relies on the sequential structure and does not extend to parallel repetition. We use a different proof approach to establish security of the commitment modification for a parallel BB84-based QPV protocol. Against bounded-entanglement adversaries, the acceptance probability decays exponentially in the minimum number $k$ of successfully committed qubits. The protocol tolerates arbitrary transmission loss and noise rates up to 3.7%, while allowing arbitrarily slow quantum communication. This yields a fully loss-tolerant, single-execution QPV protocol secure against bounded-entanglement attacks, removing transmission loss as a fundamental limitation on verification distance. We also revisit sequential repetition, correcting the treatment of conditioning on commitment and replacing the earlier conditional guarantee with an unconditional security bound, without the finite-size correction to the correctness gap. The resulting bound provides improved quantitative security parameters for experimental implementations.

quant-pharXiv:2606.25037•Jun 25, 2026•0 citations

Breaking simple quantum position verification protocols with little entanglement

Andrea Olivo, Ulysse Chabaud, André Chailloux +1 more

Instantaneous nonlocal quantum computation (INQC) evades apparent quantum and relativistic constraints and allows to attack generic quantum position verification (QPV) protocols (aiming at securely certifying the location of a distant prover) at an exponential entanglement cost. We consider adversaries sharing maximally entangled pairs of qudits and find low-dimensional INQC attacks against the simple practical family of QPV protocols based on single photons polarized at an angle $θ$. We find exact attacks against some rational angles, including some sitting outside of the Clifford hierarchy (e.g. $π/6$), and show no $θ$ allows to tolerate errors higher than $\simeq 5\cdot 10^{-3}$ against adversaries holding two ebits per protocol's qubit.

arXiv:2007.15808•Jul 31, 2020•3 citations
In quantum position verification (QPV), a prover certifies her location to a set of verifiers by performing a quantum computation. One of the first QPV protocols was proposed by Kent, Munro, and Spiller in 2011: the prover receives a qubit QQQ from one direction, receives an orthogonal basis {v,v⊥}\{ v, v^\perp \}{v,v⊥} from the opposite direction, then measures QQQ in {v,v⊥}\{ v, v^\perp \}{v,v⊥} and broadcasts the result. Several variants of this protocol have been proposed and analyzed, but the question of whether the original protocol is secure has never been fully resolved. In this work we show that there is no perfect finite-dimensional cheating strategy for the single-qubit measurement protocol. Our proof uses tools from real algebraic geometry.
Abstract We discuss quantum position verification (QPV) protocols in which the verifiers create and send single-qubit states to the prover. QPV protocols using single-qubit states are known to be insecure against adversaries that share a small number of entangled qubits. We introduce QPV protocols that are practically secure: they only require single-qubit states from each of the verifiers, yet their security is broken if the adversaries sharing an impractically large number of entangled qubits employ teleportation-based attacks. These protocols are a modification of known QPV protocols in which we include a classical random oracle without altering the amount of quantum resources needed by the verifiers. We present a cheating strategy that requires a number of entangled qubits shared among the adversaries that grows exponentially with the size of the classical input of the random oracle.
Abstract Quantum position verification (QPV) enables multiple verifiers to certify a prover’s location using quantum communication and physical assumptions. With experimental demonstrations of QPV becoming increasingly feasible, enhancing the practicality and security of QPV protocols is more important than ever. In this work, we make three key contributions toward this goal. First, we introduce a robust QPV protocol in which the verifier’s state preparation is independent of channel loss, improving reliability in real-world conditions. Second, we refine existing security analysis techniques to bolster protocol resilience against experimental imperfections. Third, we identify and address some implicit assumptions present in existing security analyses, providing a framework to eliminate such assumptions. Additionally, as an example of QPV application beyond location verification, we illustrate how QPV can be leveraged for authenticating classical communication in quantum key distribution.
Quantum position verification in one shot: parallel repetition of the fff-BB84 and fff-routing protocols
Quantum position verification (QPV) aims to verify an untrusted prover's location by timing communication with them. To reduce uncertainty, it is desirable for this verification to occur in a single round. However, previous protocols achieving one-round secure QPV had critical drawbacks: attackers pre-sharing an EPR pair per qubit could perfectly break them, and their security depended on quantum information traveling at the speed of light in vacuum, a major experimental challenge in quantum networks. In this work, we prove that a single round of interaction suffices for secure position verification while overcoming these limitations. We show that security for a one-round protocol can rely only on the size of the classical information rather than quantum resources, making implementation more feasible, even with a qubit error tolerance of up to 3.6%, which is experimentally achievable with current technology -- and showing that the timing constraints have to apply only to classical communication. In short, we establish parallel repetition of the fff-BB84 and fff-routing QPV protocols. As a consequence of our techniques, we also demonstrate an order-of-magnitude improvement in the error tolerance for the sequential repetition version of these protocols, compared to the previous bounds of Nature Physics 18, 623-626 (2022).
While it is known that unconditionally secure position-based cryptography is impossible both in the classical and the quantum setting, it has been shown that some quantum protocols for position verification are secure against attackers which share a quantum state of bounded dimension. In this work, we consider the security of two protocols for quantum position verification that combine a single qubit with classical strings of total length 2n2n2n: The qubit routing protocol, where the classical information prescribes the qubit's destination, and a variant of the BB84-protocol for position verification, where the classical information prescribes in which basis the qubit should be measured. We show that either protocol is secure for a randomly chosen function if each of the attackers holds at most n/2−5n/2 - 5n/2−5 qubits. With this, we show for the first time that there exists a quantum position verification protocol where the ratio between the quantum resources an honest prover needs and the quantum resources the attackers need to break the protocol is unbounded. The verifiers need only increase the amount of classical resources to force the attackers to use more quantum resources. Concrete efficient functions for both protocols are also given -- at the expense of a weaker but still unbounded ratio of quantum resources for successful attackers. Finally, we show that both protocols are robust with respect to noise, making them appealing for applications.
Quantum position verification (QPV) aims to certify the location of an untrusted prover, but faces two major obstacles: fundamentally, entanglement-based attacks and, experimentally, photon loss. A commitment-based modification introduced in Phys. Rev. Lett. 135, 260801 addresses both in sequentially repeated protocols. Its security analysis, however, relies on the sequential structure and does not extend to parallel repetition. We use a different proof approach to establish security of the commitment modification for a parallel BB84-based QPV protocol. Against bounded-entanglement adversaries, the acceptance probability decays exponentially in the minimum number kkk of successfully committed qubits. The protocol tolerates arbitrary transmission loss and noise rates up to 3.7%, while allowing arbitrarily slow quantum communication. This yields a fully loss-tolerant, single-execution QPV protocol secure against bounded-entanglement attacks, removing transmission loss as a fundamental limitation on verification distance. We also revisit sequential repetition, correcting the treatment of conditioning on commitment and replacing the earlier conditional guarantee with an unconditional security bound, without the finite-size correction to the correctness gap. The resulting bound provides improved quantitative security parameters for experimental implementations.
Instantaneous nonlocal quantum computation (INQC) evades apparent quantum and relativistic constraints and allows to attack generic quantum position verification (QPV) protocols (aiming at securely certifying the location of a distant prover) at an exponential entanglement cost. We consider adversaries sharing maximally entangled pairs of qudits and find low-dimensional INQC attacks against the simple practical family of QPV protocols based on single photons polarized at an angle θθθ. We find exact attacks against some rational angles, including some sitting outside of the Clifford hierarchy (e.g. π/6π/6π/6), and show no θθθ allows to tolerate errors higher than ≃5⋅10−3\simeq 5\cdot 10^{-3}≃5⋅10−3 against adversaries holding two ebits per protocol's qubit.