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Quantum information is typically fragile under measurements and environmental coupling. Remarkably, we find that its lifetime can scale exponentially with system size when the environment is continuously monitored via midcircuit measurements—regardless of bath size. Starting from a maximally entangled state with a reference, we analytically prove this exponential scaling for typical Haar-random unitaries and confirm it through numerical simulations in both random unitary circuits and chaotic Hamiltonian systems. In the absence of bath monitoring, the lifetime exhibits a markedly different scaling: It grows at most linearly—or remains constant—with system size and decays inversely with the bath size. We further extend our findings numerically to a broad class of initial states. In the intermediate regime of partial monitoring, we identify and prove a two-scale transition, where the quantum mutual information decays logarithmically at microscopic timescales but linearly at macroscopic timescales. We discuss implications for monitored quantum circuits in the weak-measurement limit, quantum algorithms such as quantum diffusion models and quantum reservoir computing, and quantum communication. Finally, we experimentally verify the gap of persisted information on IBM Quantum hardware. 

Entanglement across distant frequency bands is a crucial resource in quantum networking. However, directly entangling crossband photons, e.g., microwave and optical, is challenging. Furthermore, distributing crossband entanglement via direct quantum transduction is fundamentally limited, regardless of input engineering with unconstrained source brightness. We propose to utilize intraband entanglement to overcome such direct-transduction limits by a factor that increases with the input intraband entanglement brightness in the ideal case. In the presence of experimental loss 5% and assuming 10 dB of squeezing in both optical and microwave bands, we show that our protocol can generate a violation of the separability criterion equivalent to 2.38 ebits, compared with the baseline protocol limited to 0.082 ebits. The proposed protocols rely only on off-the-shelf components and provide advantages robust to a substantial amount of loss. 

Quantum randomness, especially random pure states, underpins fundamental questions like black hole physics and quantum complexity, as well as in practical applications such as quantum device benchmarking and quantum advantage certification. The conventional approach for generating genuine random states, known as ‘deep thermalization’, faces significant challenges, including scalability issues due to the need for a large ancilla system and susceptibility to attacks, as demonstrated in this work. We introduce holographic deep thermalization, a secure and hardware-efficient quantum random state generator. Via a sequence of scrambling-measure-reset processes, it continuously trades space with time, and substantially reduces the required ancilla size to as small as a system-size-independent constant; at the same time, it guarantees security by eliminating quantum correlation between the data system and potential attackers. Thanks to the resource reduction, our circuit-based implementation on IBM Quantum devices achieves genuine 5-qubit random state generation utilizing only a total of 8 qubits.