Quantum information masking (QIM) allows encoding quantum information in multipartite systems. Complete QIM is of great significance in quantum foundation and application. However, the realization of complete QIM, even for single-qubit encoded information, is still lacking. Here, we propose to demonstrate complete QIM with 4-qubit entangled states. The proposed QIM can be readily extended to multipartite systems with arbitrary number of subsystems, enabling quantum secret sharing (QSS) and quantum teleportation between multiplayers. In experiment, we build up a 4-qubit hyperentangled state to implement complete QIM. The trace distance of 16 encoded single-qubit states falls within the range of 0.12 ± 0.02 to 0.03 ± 0.02. Furthermore, we implement QSS between six players by expanding the 4-qubit state to a 6-qubit state entangled in hybrid manner, in which we observe an average fidelity 0.85 ± 0.03 of the recovered states. Our results open the door towards QIM-enabled quantum information processing and provide applications in quantum communications. Quantum information masking allows encoding quantum information in multipartite systems, which is hidden from subsystems and can be recovered from the nonlocal correlation. The authors propose and realize the complete quantum information masking and apply it to quantum secret sharing between six players.
Quantum information masking (QIM) allows encoding quantum information in multipartite systems. Complete QIM is of great significance in quantum foundation and application. However, the realization of complete QIM, even for single-qubit encoded information, is still lacking. Here, we propose to demonstrate complete QIM with 4-qubit entangled states. The proposed QIM can be readily extended to multipartite systems with arbitrary number of subsystems, enabling quantum secret sharing (QSS) and quantum teleportation between multiplayers. In experiment, we build up a 4-qubit hyperentangled state to implement complete QIM. The trace distance of 16 encoded single-qubit states falls within the range of 0.12 ± 0.02 to 0.03 ± 0.02. Furthermore, we implement QSS between six players by expanding the 4-qubit state to a 6-qubit state entangled in hybrid manner, in which we observe an average fidelity 0.85 ± 0.03 of the recovered states. Our results open the door towards QIM-enabled quantum information processing and provide applications in quantum communications. Quantum information masking allows encoding quantum information in multipartite systems, which is hidden from subsystems and can be recovered from the nonlocal correlation. The authors propose and realize the complete quantum information masking and apply it to quantum secret sharing between six players.
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.
Abstract Quantum information masking (QIM) is a crucial technique for protecting quantum data from being accessed by local subsystems. In this paper, we introduce a novel method for achieving 1-uniform QIM in multipartite systems utilizing a Fourier matrix. We further extend this approach to construct an orthogonal array with the aid of a Hadamard matrix, which is a specific type of Fourier matrix. This allows us to explore the relationship between 2-uniform QIM and orthogonal arrays. Through this framework, we derive two distinct 2-uniform quantum states, enabling the 2-uniform masking of original information within multipartite systems. Furthermore, we prove that the maximum number of quantum bits required for achieving a 2-uniformly masked state is 2 n − 1, and the minimum is 2 n−1 + 3. Moreover, our scheme effectively demonstrates the rich quantum correlations between multipartite systems and has potential application value in quantum secret sharing.
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.
Masking of quantum information is a way of hiding information in correlations such that no information is accessible to any local observer. Although the set of all quantum states as a whole cannot be masked into bipartite correlations according to the no-masking theorem, the set of real states is maskable and is a maximal maskable set. In this work, we experimentally realize a masking protocol of the real ququart by virtue of a photonic quantum walk. Our experiment clearly demonstrates that quantum information of the real ququart can be completely hidden in bipartite correlations of two-qubit hybrid entangled states, which are encoded in two different degrees of freedom of a single photon. The hidden information is not accessible from each qubit alone, but can be faithfully retrieved with a fidelity of about 99% from correlation measurements. By contrast, any superset of the set of real density matrices cannot be masked.
Secret sharing is a conventional technique for realizing secure communications in information networks, where a dealer distributes to n players a secret, which can only be decoded through the cooperation of k (n/2<k≤n) players. In recent years, quantum resources have been employed to enhance security of secret sharing, which has been named quantum secret sharing (QSS). A multipartite bound entanglement (BE) state of an optical field, due to its special entanglement features, can be used in quantum networks to improve security and flexibility of communication. We design and experimentally demonstrate a QSS protocol, where the dealer modulates a secret on a four-partite BE state and then distributes the submodes of the BE state to four spatially separated players. The presented QSS scheme has the capability to protect secrets from eavesdropping and dishonest players, because a nonlocal and deterministic BE state is shared among four authorized players.
Masking of quantum information spreads it over nonlocal correlations and hides it from the subsystems. It is known that no operation can simultaneously mask all pure states [Phys. Rev. Lett. 120, 230501 (2018)PRLTAO0031-900710.1103/PhysRevLett.120.230501], so in what sense is quantum information masking useful? Here, we extend the definition of quantum information masking to general mixed states, and show that the resource of maskable quantum states is far more abundant than the no-go theorem seemingly suggests. Geometrically, the simultaneously maskable states lays on hyperdisks in the state hypersphere, and strictly contains the broadcastable states. We devise a photonic quantum information masking machine using time-correlated photons to experimentally investigate the properties of qubit masking, and demonstrate the transfer of quantum information into bipartite correlations and its faithful retrieval. The versatile masking machine has decent extensibility, and may be applicable to quantum secret sharing and fault-tolerant quantum communication. Our results provide some insights on the comprehension and potential application of quantum information masking.