No-cloning theorem in quantum cryptography prevents an eavesdropper from perfectly duplicating any arbitrary quantum state. Here we argue that an experimental scheme to produce a quantum superposition of interacting Bose-Einstein condensates can generate N bosonic clones of any arbitrary single quantum state at large N limit of thermodynamic equilibrium with high fidelity and thus operationally ‘bypass’ the restrictions imposed by the above mentioned theorem. This is possible because quantum statistical nature of this ‘cloning operation’ does not require strict unitary evolution of standard quantum mechanics within a single Hilbert space.
No-cloning theorem in quantum cryptography prevents an eavesdropper from perfectly duplicating any arbitrary quantum state. Here we argue that an experimental scheme to produce a quantum superposition of interacting Bose-Einstein condensates can generate N bosonic clones of any arbitrary single quantum state at large N limit of thermodynamic equilibrium with high fidelity and thus operationally ‘bypass’ the restrictions imposed by the above mentioned theorem. This is possible because quantum statistical nature of this ‘cloning operation’ does not require strict unitary evolution of standard quantum mechanics within a single Hilbert space.
No-cloning theorem in quantum cryptography prevents an eavesdropper from perfectly duplicating any arbitrary quantum state. Here we argue that an experimental scheme to produce a quantum superposition of interacting Bose-Einstein condensates can generate N bosonic clones of any arbitrary single quantum state at large N limit of thermodynamic equilibrium with high fidelity and thus operationally ‘bypass’ the restrictions imposed by the above mentioned theorem. This is possible because quantum statistical nature of this ‘cloning operation’ does not require strict unitary evolution of standard quantum mechanics within a single Hilbert space.
The No Cloning theorem in quantum cryptography prevents any eavesdropper from exactly duplicating an arbitrary quantum superposition state of a single photon. Here we argue that an experimental scheme to produce an interacting, two component Bose-Einstein condensates can, in principle, generate macroscopically large number of bosonic clones of any arbitrary single photon wave packet with high fidelity at large N limit of thermodynamic equilibrium using excitons or electron hole pairs. It is possible, because initially one can isolate the two orthogonal polarizations using polarizing beam splitters and then amplify the corresponding single photon wave packets identically but separately. This is to ensure that the amplified beams can be used to generate proportionately same, yet large numbers of bosons to produce two distinct but interacting condensates using additional light matter interactions within a semiconductor structure. One can then extract the cloned photons once the identical excitons in the two-component quantum ground state of the condensate radiatively recombine. Thus the overall cloning process can operationally bypass the restrictions imposed by the above mentioned theorem. This is because the quantum statistical nature of this proposed cloning operation does not require any strict unitary evolution of standard quantum mechanics within a single Hilbert space.
Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. Although perfect copies are prohibited, a quantum state may be copied with maximal accuracy via various optimal cloning schemes. Optimal quantum cloning, which lies at the border of the physical limit imposed by the no-signaling theorem and the Heisenberg uncertainty principle, has been experimentally realized for low-dimensional photonic states. However, an increase in the dimensionality of quantum systems is greatly beneficial to quantum computation and communication protocols. Nonetheless, no experimental demonstration of optimal cloning machines has hitherto been shown for high-dimensional quantum systems. We perform optimal cloning of high-dimensional photonic states by means of the symmetrization method. We show the universality of our technique by conducting cloning of numerous arbitrary input states and fully characterize our cloning machine by performing quantum state tomography on cloned photons. In addition, a cloning attack on a Bennett and Brassard (BB84) quantum key distribution protocol is experimentally demonstrated to reveal the robustness of high-dimensional states in quantum cryptography.
The no-cloning theorem forbids the creation of identical copies of qubits, thereby imposing strong limitations on quantum technologies. A recently-proposed protocol, encrypted cloning, showed, however, that the creation of perfect clones is theoretically possible - if the clones are simultaneously encrypted with a single-use decryption key. It has remained an open question, however, whether encrypted cloning is stable under hardware noise and thus practical as a quantum primitive. This is nontrivial because spreading quantum information widely could dilute it until barely exceeding the noise level, leading to catastrophic fidelity decay. Given the complexity of hardware noise, theory and classical simulation are insufficient to settle this. Here, we settle this question experimentally, on IBM Heron-R2 superconducting processors using up to 154 qubits. We find that encrypted cloning is stable under hardware noise, even when used as a module, namely in parallel, series or interleaved, while preserving pre-existing entanglement. This establishes it as a versatile quantum primitive for practical use, and it necessitates a refinement to our understanding of the no-cloning theorem: quantum information can be spread at will, in theory and in practice, without dilution or degradation, if encrypted or obscured. The actual constraint is that the decryption mechanism must be single-use.
Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. Although such perfect copies are prohibited, a quantum state may be copied with maximal accuracy via various optimal cloning schemes. Optimal quantum cloning, which lies at the border of the physical limit imposed by the no-signalling theorem and the Heisenberg uncertainty principle, has been experimentally realized for low dimensional photonic states. However, an increase in the dimensionality of quantum systems is greatly beneficial to quantum computation and communication protocols. Nonetheless, no experimental demonstration of optimal cloning machines has hitherto been shown for high-dimensional quantum systems. Here, we perform optimal cloning of high-dimensional photonic states by means of the symmetrization method. We show the universality of our technique by conducting cloning of numerous arbitrary input states, and fully characterize our cloning machine by performing quantum state tomography on \emph{cloned} photons. In addition, a cloning attack on a Bennett and Brassard (BB84) quantum key distribution protocol is experimentally demonstrated in order to reveal the robustness of high-dimensional states in quantum cryptography.
Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context, the fundamental quantum limit to the quality of the clones is imposed by the unavoidable presence of spontaneous emission. In our experiment, a single input photon stimulates the emission of additional photons from a source on the basis of parametric down-conversion. This leads to the production of quantum clones with near-optimal fidelity. We also demonstrate universality of the copying procedure by showing that the same fidelity is achieved for arbitrary input states.