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arXiv:2209.12261 · Physical Review A

No-masking theorem for observables

Swapnil Bhowmick, Abhay Srivastav, Arun Kumar Pati

Published Aug 15, 2024• 2 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1103/physreva.110.022423

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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 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.
It is impossible to mask an arbitrary quantum state into the correlations between two subsystems such that the original information is completely unknown to each local system. This is the no-masking theorem proposed by Modi et al. [K. Modi, A. K. Pati, A. Sen(De), and U. Sen, Phys. Rev. Lett. 120, 230501 (2018)]. In this work, we propose the concept of kkk-uniform quantum information masking in multipartite systems and indicate the relation between quantum error-correcting codes (QECCs) in heterogeneous systems and quantum information masking. As a consequence, we show that the no-masking theorem is a special case of the quantum Singleton bound for QECCs in heterogeneous systems essentially, and we give a more general no-masking theorem in multipartite systems based on the quantum Singleton bound. We also solve two open questions proposed by Li and Wang [M.-S. Li and Y.-L. Wang, Phys. Rev. A 98, 062306 (2018)]. That is, an arbitrary state of level ddd cannot be masked in a tripartite system of level ddd such that the marginal states are not proportional to identity, and an arbitrary state of level ddd cannot be masked in a tripartite system of level nnn with n<dn<dn<d. Further, we give some methods for constructing new QECCs from old QECCs in heterogeneous systems.
Abstract Quantum information masking is a protocol that hides the original quantum information from subsystems and spreads it over quantum correlation, which is available to multipartite except bipartite systems. In this work, we explicitly study the quantum information masking in multipartite scenario and prove that there exists an universal quantum masker can mask the information encoding in the unknown states into a multipartite system with lower-dimensional local systems, namely, all the k-level quantum states can be masked into a m-qudit systems (m ≥ 4) whose local dimension d ≤ k . In order to observe the masking process intuitively, explicitly controlled operations are provided. Our scheme well demonstrates the abundance of quantum correlation between multipartite quantum system and has potential application in the security of quantum information processing.
The no-masking theorem says that masking quantum information is impossible in a bipartite scenario. However, there exist schemes to mask quantum states in multipartite systems. In this work, we show that, the joint measurement in the teleportation is really a masking process, when the apparatus is regarded as a quantum participant in the whole system. Based on the view, we present two four-partite maskers and a tripartite masker. One of the former provides a generalization in arbitrary dimension of the four-qubit scheme given by Li and Wang [Phys. Rev. A 98, 062306 (2018)], and the latter is precisely their tripartite scheme. The occupation probabilities and coherence of quantum states are masked in two steps of our schemes. And the information can be extracted naturally in their reverse processes.
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.