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arXiv:2308.11626 · Results in Physics

No-masking does not imply no commitment

Guang Ping He

Published Jan 15, 2024• 0 citations
arXivHTMLPDF

Abstract

The no-masking theorem claims that arbitrary quantum states cannot be masked. Based on this result, it was further claimed that qubit commitment is impossible. However, here we show that arbitrary known quantum states can be masked. Meanwhile, the states in qubit commitment is always known. Consequently, the no-masking theorem cannot lead to no qubit commitment.

DOI
10.1016/j.rinp.2024.107346

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Abstract Quantum information masking (QIM) entails the transmission of quantum information from a single qubit to the entanglement within quantum system, demonstrating promise for utilization in quantum communication. However, the absence of a universal masker capable of masking all qubits restricts its utility in quantum communication and poses a threat to information security. Here we successfully implement the improved QIM method by designing a quantum masking machine capable of masking the set of states on arbitrary disks. The analysis of several sets of target-qubit states proves that our study extends the range of maskable sets in QIM. Through this approach, we devise a scheme for quantum secret sharing (QSS) and demonstrate its feasibility using a proof-of principle experiment. This research results not only provides new experimental evidence for QIM, but also lays a solid foundation for its application in quantum communication.1. IntroductionThroughout history, reliable and secure communication has been crucial for the development and even survival of individuals and nations. Classical cryptosystems rely on computational complexity for encryption, while quantum cryptography [1, 2] leverages the principles of quantum information to offer enhanced levels of security [3–5].Various no-go theorems are essential for improving the security and integrity of quantum communication [6–14]. These theorems imply that certain operations that cannot be performed on quantum states used for transmitting information, such as the no-cloning theorem [15–17], the no-broadcasting theorem [18], the no-deleting theorem [19] and the no-hiding theorem [20, 21], etc. A new no-go theorem, known as the no-masking theorem [22], has recently been discovered and proven in relation to the quantum information masking (QIM) [23–30], a technique utilized for transferring information stored in a single qubit to the entanglement of a multi-qubit system. The no-masking theorem demonstrates that there is no universal masker capable of masking all states of a qubit in two-dimensional Hilbert space. For example, the analysis of the maskable sets shows that only quantum information stored strictly in phase can be masked by one masker. This limitation poses a potential security risk in quantum communication, as unmasked information (e.g., latitude of the Bloch sphere) could be exploited by eavesdroppers.In this paper, we proposes an improved QIM method to mask the set of qubit states on any Bloch sphere disk using a single masker and experimentally demonstrates a QSS scheme based on this approach. This approach can extends the range of maskable sets for QIM by utilizing an adapter to aid a single masker in building the improved quantum masking machine. In particular, we ingeniously apply these maskable sets to QSS to prevent hackers from inferring the transmission state solely from the single reduced qubit, while still allowing both parties to extract information from entanglement for secure communication. Our single-photon experiments have clearly demonstrated how QSS can be effectively implemented on an improved quantum information masking machine, enabling the transmission of a set of quantum states across an arbitrary disk. Our research extends the scope of maskable sets in QIM, proposes a QSS scheme based on these sets, and experimentally verifies its feasibility, thereby expanding the potential applications of QIM.

•Sep 4, 2025•0 citations
The no-masking theorem claims that arbitrary quantum states cannot be masked. Based on this result, it was further claimed that qubit commitment is impossible. However, here we show that arbitrary known quantum states can be masked. Meanwhile, the states in qubit commitment is always known. Consequently, the no-masking theorem cannot lead to no qubit commitment.
Classical information encoded in composite quantum states can be completely hidden from the reduced subsystems and may be found only in the correlations. Can the same be true for quantum information? If quantum information is hidden from subsystems and spread over quantum correlation, we call it masking of quantum information. We show that while this may still be true for some restricted sets of nonorthogonal quantum states, it is not possible for arbitrary quantum states. This result suggests that quantum qubit commitment-a stronger version of the quantum bit commitment-is not possible in general. Our findings may have potential applications in secret sharing and future quantum communication protocols.
The no-masking theorem for quantum information proves that it is impossible to encode an arbitrary input state into a larger bipartite entangled state such that the full information is stored in the correlation but the individual subsystems have no information about the input state. Here, we ask the question: Is it possible to mask an observable such that the information about the observable is available in the joint system, but individual subsystems reveal nothing about the imprints of the observable? This generalizes the notion of masking to observables. We show that a universal unitary that can mask an arbitrary observable in any dimension does not exist. For a qubit system, we show that the masking operation for a given observable is locally unitarily connected to the swap operation. This suggests a conservation law for information content of observables that goes beyond the conservation laws under symmetry operations. Furthermore, we prove that the unconditional no-bit commitment result follows from the no-masking theorem for observables. Our results can have important applications in quantum information and quantum communication where we encode information not in states but in observables.
A commitment scheme allows one to commit to hidden information while keeping its value recoverable when needed. Despite considerable efforts, an unconditionally and perfectly secure bit commitment has been proven impossible both classically and quantum-mechanically. The situation is similar when committing to qubits instead of classical bits as implied in the no-masking theorem [K. Modi et al., Phys. Rev. Lett. {\bf 120}, 230501 (2018)]. In this Letter, we find that circumvention of the no-masking theorem is possible with the aid of classical randomness. Based on this, we construct an unconditionally secure quit-commitment scheme that utilises any kind of universal quantum maskers with optimal randomness consumption, which is distributed by a trusted initializer. This shows that randomness, which is normally considered only to obscure the information, can benefit a quantum secure communication scheme. This result can be generalised to an arbitrary dimensional system.
To solve the problem of hiding quantum information in simplified subsystems, Modi et al. [1] introduced the concept of quantum masking. Quantum masking is the encoding of quantum information by composite quantum states in such a way that the quantum information is hidden to the subsystem and spreads to the correlation of the composite systems. The concept of quantum masking was developed along with a new quantum impossibility theorem, the quantum no-masking theorem. The question of whether a quantum state can be masked has been studied by many people from the perspective of the types of quantum states, the number of masking participants, and error correction codes. Others have studied the relationships between maskable quantum states, the deterministic and probabilistic masking of quantum states, and the problem of probabilistic masking. Quantum masking techniques have been shown to outperform previous strategies in quantum bit commitment, quantum multi-party secret sharing, and so on.
Abstract Quantum information masking (QIM) entails the transmission of quantum information from a single qubit to the entanglement within quantum system, demonstrating promise for utilization in quantum communication. However, the absence of a universal masker capable of masking all qubits restricts its utility in quantum communication and poses a threat to information security. Here we successfully implement the improved QIM method by designing a quantum masking machine capable of masking the set of states on arbitrary disks. The analysis of several sets of target-qubit states proves that our study extends the range of maskable sets in QIM. Through this approach, we devise a scheme for quantum secret sharing (QSS) and demonstrate its feasibility using a proof-of principle experiment. This research results not only provides new experimental evidence for QIM, but also lays a solid foundation for its application in quantum communication.1. IntroductionThroughout history, reliable and secure communication has been crucial for the development and even survival of individuals and nations. Classical cryptosystems rely on computational complexity for encryption, while quantum cryptography [1, 2] leverages the principles of quantum information to offer enhanced levels of security [3–5].Various no-go theorems are essential for improving the security and integrity of quantum communication [6–14]. These theorems imply that certain operations that cannot be performed on quantum states used for transmitting information, such as the no-cloning theorem [15–17], the no-broadcasting theorem [18], the no-deleting theorem [19] and the no-hiding theorem [20, 21], etc. A new no-go theorem, known as the no-masking theorem [22], has recently been discovered and proven in relation to the quantum information masking (QIM) [23–30], a technique utilized for transferring information stored in a single qubit to the entanglement of a multi-qubit system. The no-masking theorem demonstrates that there is no universal masker capable of masking all states of a qubit in two-dimensional Hilbert space. For example, the analysis of the maskable sets shows that only quantum information stored strictly in phase can be masked by one masker. This limitation poses a potential security risk in quantum communication, as unmasked information (e.g., latitude of the Bloch sphere) could be exploited by eavesdroppers.In this paper, we proposes an improved QIM method to mask the set of qubit states on any Bloch sphere disk using a single masker and experimentally demonstrates a QSS scheme based on this approach. This approach can extends the range of maskable sets for QIM by utilizing an adapter to aid a single masker in building the improved quantum masking machine. In particular, we ingeniously apply these maskable sets to QSS to prevent hackers from inferring the transmission state solely from the single reduced qubit, while still allowing both parties to extract information from entanglement for secure communication. Our single-photon experiments have clearly demonstrated how QSS can be effectively implemented on an improved quantum information masking machine, enabling the transmission of a set of quantum states across an arbitrary disk. Our research extends the scope of maskable sets in QIM, proposes a QSS scheme based on these sets, and experimentally verifies its feasibility, thereby expanding the potential applications of QIM.