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We investigate multiparameter quantum estimation in a molecular dimer composed of two dipole dipole interacting two level systems, focusing on the simultaneous estimation of temperature $T$ and detuning $Λ$. By employing a vectorization approach to derive the quantum Fisher information matrix, we analyze the precision limits of both simultaneous and individual estimation strategies. We show that simultaneous estim...
Which properties of a quantum many body system are operationally accessible is a central question underlying spectroscopy, thermodynamics, and quantum information science. Conventional response theory answers this question within a system only paradigm: one perturbs and measures the matter itself, obtaining susceptibility built from causally ordered nested commutators. Here we show that coherently controlled quant...
We investigate the resilience to noise of single qubit quantum key distribution (QKD) protocols in the scenario of security against independent eavesdropping attacks and key distillation based on one way classical communication. To this end, we introduce a noise based metric that quantifies the efficiency of QKD protocols. Within this framework, we analyze the maximal noise levels that allow Alice and Bob to asymp...
A study published on bioRxiv demonstrates an ultra low latency quantum decoding approach for BCI neural signals utilizing a physical 1000 qubit coherent photonic Ising machine (CIM). By mapping neural spike patterns onto Ising Hamiltonians, the hardware native Quantum Semi Restricted Boltzmann Machine (QSRBM) achieved up to 96.2% decoding accuracy across actual in vivo data. By performing inference through hardwar...
The realization of long distance quantum communication and the envisioned quantum internet relies on coherent hybrid light matter interfaces connecting quantum light emitters with quantum memory (QM) systems. Unlike probabilistic photon pair sources such as spontaneous parametric down conversion, deterministic quantum light emitters enable the on demand production of pure and bright single and entangled photons, e...
Extending and refining a preceding work, the free evolution of a quantum wave function, with fixed initial and final modulus, is considered in the general case where nodes are allowed. The method is based on considering a suitable simple functional related to the quadratic optimal transport cost in discrete time. Under reasonable assumptions it is shown that, if nodes are present, the free evolution of the wave fu...
Partial differential equations are a promising application area for fault tolerant quantum algorithms, but the subject lies between two communities with different languages: numerical analysis and quantum computation. These lecture notes provide a numerically grounded introduction for readers entering from either field. Block encoding is the organizing principle: once a discretized differential operator is embedde...
We expand on the ideas developed by C. Jarzynski in Physica A 552, 122077 (2020), where an integral fluctuation theorem was derived with the aim of obtaining thermodynamic inequalities stronger than those implied by the Jarzynski equality. Restricting ourselves to the quantum setting, we derive the corresponding detailed fluctuation theorem and additional detailed and integral fluctuation theorems; we also provide...
Imaginary time evolution (ITE) is a powerful method for ground state preparation of a given Hamiltonian. The normalized ITE can be viewed as a gradient flow of the energy expectation value with respect to the Fubini Study metric. In this work, we propose a generalized nonlinear imaginary time evolution (NITE) for more general quantum state preparation tasks. We further present a hardware efficient variational impl...
We investigate Unruh DeWitt detectors coupled to composite observables of a quantum scalar field, including quadratic coupling to the field momentum and coupling to the local energy density. We develop a distributional framework for evaluating the corresponding detector response functions and apply it to detectors crossing the Rindler firewall. While we recover the finite response of the derivative coupling model,...
Quantum information theory (QIT) characterizes the capabilities and fundamental limits of quantum information processing, underpinning quantum communication, computation, and error correction. Formalizing its coding theorems requires connecting finite block protocols, analytic inequalities, and asymptotic limits within a unified machine checked framework. Existing developments, however, lack a reusable operational...
We revisit von Neumann's theory of infinite tensor products of Hilbert spaces. On the set $Γ$ of equivalence classes of $C 0$ sequences, which labels the incomplete tensor products inside the complete tensor product, we introduce a natural pseudo ultrametric $d$: the distance between two classes is the convergence exponent of the series $\sum j|\langle\varphi j,ψ j\rangle 1|$ formed from any pair of representative...
Many production quantum programming languages represent hybrid quantum computations by extending a classical base language with a quantum effect, where qubits are addressed by reference, and quantum operations are understood to mutate some external quantum state. However, the semantics of this view of quantum computation remains underdeveloped, especially when the language allows mid circuit measurements and non t...
Active selection of the measurement basis underpins quantum protocols including device independent quantum key distribution, quantum teleportation with active feed forward, and Bell tests. High speed operation is crucial to minimize the latency between consecutive measurement choices, enabling faster protocol execution and higher achievable communication rates. Here, we demonstrate a GHz rate all fiber polarizatio...
Tunneling is essential in the initialization, measurement, and control of quantum dot qubits. In silicon, such tunneling connects not only the qubit states but also valley minima in the conduction band on opposite sides of the Brillouin zone, with large consequences for the quantum dot behavior. Here we present a full characterization of the intravalley and intervalley tunnel couplings, including their complex pha...
We propose a novel formulation of master equations for open systems wherein the evolution of a state is determined solely by its local behaviour at any point of time. Specifically, our formulation allows for a local interpretation of the workings of beyond Markovian dynamics as opposed to the more common conception that non Markovian state evolution is affected by its cumulative past history. Quite interestingly, ...
Cavity optomagnomechanics provides a versatile platform to explore macroscopic quantum correlations, particularly nonreciprocal entanglement. In this work, we propose a theoretical scheme to generate switchable bipartite and tripartite entanglement in an optomagnomechanical ring cavity by exploiting phase controlled magnon squeezing. Indeed, two spatially separated ferrimagnetic YIG microbridges become entangled t...
The black hole information paradox has motivated extensive study of how and when information escapes from evaporating black holes. Here we address the analogous question for cosmological horizons: when does an individual Hawking pair begin to carry information out of a de Sitter horizon? We study this problem in a class of two dimensional flow geometries that interpolate smoothly between an asymptotic AdS$ 2 $ bou...
Whether a heat engine can approach Carnot efficiency while maintaining finite power is a fundamental question in finite time thermodynamics. For classical Markovian heat engines with local interactions, the power efficiency trade off forbids an asymptotic approach to Carnot efficiency at finite power. In quantum systems, by contrast, degeneracy, symmetry, and collective jumps have been theoretically predicted to e...
Phenomena that slip beyond the grasp of our classical intuition reveal uniquely quantum effects that deepen our understanding of the physical world and enable advances in information processing, particularly in quantum communication and computation. One such phenomenon is quantum steering, whereby measurements performed by one party influence the conditional states of another when the two share an entangled quantu...
