arXiv subjects

Arash Azizi

Publications and source records attributed to Arash Azizi.

At least 19 recordsLinked to original sources

arXiv2026

Quantum Fisher information and quadrature squeezing in Janus superpositions of squeezed vacua

Janus states, defined as coherent superpositions of two single-mode squeezed vacua, provide a simple but genuinely non-Gaussian setting for studying how interference reshapes quantum Fisher information (QFI) beyond the Gaussian squeezed-vacuum picture. Using an exact analytic treatment, we determine the QFI of Janus states and identify the benchmarks under which they can or cannot offer a metrological advantage over the single squeezed vacuum. We find that, under a fair comparison at fixed mean photon number, the single squeezed vacuum remains optimal for principal second-moment squeezing, so no genuine Janus advantage exists at that level. By contrast, within a fixed two-state span, a Janus superposition can simultaneously outperform its constituents in a laboratory quadrature variance and in number-generated phase QFI. We also introduce an operational benchmark based on fixed measured squeezing and show that, at the same observed squeezing level, Janus interference can substantially enhance the QFI for quadratic-generator sensing beyond the pure-Gaussian squeezed-vacuum reference. These results show that the metrological performance of Janus states is controlled not only by quadrature squeezing, but also by higher-order fluctuations and by the benchmark used for comparison.

quant-ph↗

arXiv2026

Worldline-Induced Transparency

We show that the Unruh response can be interferometrically suppressed or restored in a single Unruh--DeWitt detector whose center-of-mass is prepared in a coherent superposition of two uniformly accelerated worldlines. The two paths remain physically disjoint; the detector is read out in a path-erasing basis so that no which-path information is revealed. If the detector's energy gap is path dependent during the interaction, the branch amplitudes for first-order excitation become operationally indistinguishable and therefore add coherently. With appropriate tuning -- matching the gap-to-acceleration ratios of the two branches and choosing a single relative phase -- the conditional first-order excitation amplitude cancels, while reversing the phase restores the response. We derive these conditions in two complementary formalisms and interpret the mechanism as a relativistic analogue of electromagnetically induced transparency, which we term worldline-induced transparency. We also treat finite switching times explicitly and quantify how imperfect matching produces a residual signal, yielding a tolerance window rather than an idealized infinitely sharp condition.

hep-th↗

arXiv2026

Saving the Unruh Signal: Coherent Cancellation of Spontaneous Emission with Entangled Detectors

The Unruh effect is notoriously difficult to detect, as it is exponentially overwhelmed by Wigner--Weisskopf spontaneous emission. We show that this fundamental obstacle can be overcome by harnessing multi-detector quantum interference. By preparing a system of three entangled Unruh--DeWitt detectors in a specific W-state, the spontaneous emission channels can be forced to destructively interfere and vanish, thereby "saving" the Unruh signal by coherently silencing this dominant noise. Our central result is the derivation of the condition for complete and simultaneous cancellation of all right- and left-traveling emission modes. We find this requires preparing the detectors in a unique entangled state whose real-valued coefficients are fixed by an elegant geometric constraint, given by a ratio of sines of the logarithms of the detector accelerations. This work establishes multi-detector entanglement as a precision tool for noise cancellation in relativistic quantum settings, offering a new pathway toward the definitive observation of the Unruh signal.

gr-qc↗

arXiv2025

Two-Mode Janus States: non-Gaussian generalizations of thermofield double

We introduce the Two-Mode Janus State (TMJS), a non-Gaussian quantum state defined as a coherent superposition of two distinct Two-Mode Squeezed States (TMSS). This construction serves as a direct, non-Gaussian generalization of the canonical thermofield double (TFD) state, which is itself a single, Gaussian TMSS. We develop a complete analytical framework for the TMJS's arbitrary $k$-th order photon statistics, identifying a new family of "squeezing polynomials" that govern all diagonal and off-diagonal moments. Our central result is that the state's non-Gaussianity is dynamically steerable via an external "Janus phase." This phase acts as a switch, allowing the higher-order coherences ($g^{(k)}$) to be tuned from perfectly thermal (matching the TFD marginal) to deeply sub-Poissonian, a regime marked by strong Wigner negativity. We further establish a physical realization for the TMJS, proposing its generation via coherently superposed Dynamical Casimir Effect (DCE) trajectories, distinguishing it from the static, observer-dependent Unruh effect. The TMJS provides a versatile, interference-enhanced platform for engineering Unruh-DeWitt detector responses and probing non-Gaussian physics in relativistic settings.

quant-ph↗

arXiv2025

Two-Photon Emission from an Accelerated Detector with Gaussian Switching

We present a closed-form analysis of second-order two-photon emission from a uniformly accelerated Unruh-DeWitt detector with a smooth Gaussian switch and derivative coupling. The time-ordered Dyson integrals are evaluated exactly, yielding a single spectral amplitude that simultaneously covers all four channels--right-travelling/right-travelling (RR), left-travelling/left-travelling (LL), right-travelling/left-travelling (RL), and left-travelling/right-travelling (LR). The spectra are organized by narrow kinematic gates (sum-frequency for RR/LL, difference-frequency for RL/LR) and a causal resonant denominator encoded by the Faddeeva function. As the gate time increases, the Gaussian factors sharpen into delta constraints and recover the eternal-interaction response. We map scaling with acceleration, gap, and duration, and show that the single-particle marginal combines a sharp nonthermal resonance with an Unruh thermal tail.

physics.gen-ph↗

arXiv2025

Modulated Accelerating Mirrors as a Physical Realization of the Kappa-Gamma Vacuum

Modulated accelerating mirrors provide a concrete dynamical origin for the $\kappa\gamma$ vacuum-a thermal, single-mode squeezed state with a tunable angle. The Carlitz-Willey trajectory fixes the Planckian weights (set by $\kappa$), while a weak, chiral, frequency-diagonal boundary drive-equivalently a time-dependent Robin impedance-rotates the squeeze angle (set by $\gamma$) without changing those weights at leading order. On future null infinity, the two-point function cleanly splits into a stationary thermal piece and a phase-sensitive, non-stationary piece. Inertial Unruh-DeWitt detectors see an exact Planck law; uniformly accelerated detectors expose $\gamma$ through interference and can show mode-selective suppression under frequency matching. Numerical wave-packet simulations corroborate the phase imprint and parametric amplification. In short: trajectory sets scale, boundary sets angle. This separation turns abstract squeeze parameters into laboratory-tunable signatures and offers a practical route to engineer and diagnose $\kappa\gamma$ vacua in moving-mirror analogs.

hep-th↗

arXiv2025

The Kerr-Induced Superradiant Tricritical Point

The interplay of interaction and dissipation in open quantum systems can forge phase transitions beyond conventional paradigms. In the canonical quantum Rabi model, we demonstrate that a photon-photon (Kerr) interaction transforms the celebrated superradiant phase transition, inducing a line that separates continuous, second-order behavior from discontinuous, first-order regimes. Strikingly, this is not a line of tricritical points. Instead, we prove that genuine tricriticality is an isolated phenomenon, emerging only at a single, mathematically exact dissipation rate: the ``sweet spot'' of $\kappa_t^2 = (\sqrt{13}-2)/3$. Our discovery pinpoints the precise and restrictive conditions for realizing a rare multicritical point in a foundational quantum optical system, identifying this critical dissipation as a unique gateway to a higher order of criticality.

quant-ph↗

arXiv2025

Exponentially accelerated mirrors as a physical realization of the kappa plane-wave vacuum

The kappa plane-wave vacuum is a family of kinematically defined quantum states whose thermal properties are well understood, but whose physical origin has remained obscure. In this paper we provide a concrete dynamical realization of this vacuum, showing that it is physically and operationally equivalent to the quantum state produced on future null infinity by a mirror following the Carlitz-Willey (CW) trajectory. The equivalence is established through a three-pronged analysis: we demonstrate that the two constructions share identical Bogoliubov squeeze parameters, identical nonlocal thermal kernels in their Wightman functions, and identical Planckian responses of an Unruh-DeWitt detector. This result anchors an abstract kinematic construction in a well-understood dynamical model, identifying the parameter $\kappa$ with the physical scale that governs the Carlitz-Willey trajectory. In the final part of the paper we characterize, within the moving-mirror framework, the complete class of mirror trajectories that reproduce the same asymptotic thermal kernel on $\mathscr I^+_R$, and show that only the purely exponential CW trajectory generates a constant, stationary flux.

physics.gen-ph↗

arXiv2025

Tunable Non-Gaussianity and Exact Higher-Order Coherences for Quantum Advantage

Non-Gaussian states are essential for achieving a quantum advantage in continuous-variable (CV) information processing. Among these, coherent superpositions of squeezed states are a foundational resource. While exact higher-order statistics are available in the undisplaced case, a complete and analytically tractable treatment with a common displacement has been missing. We introduce and solve the displaced Janus state-a coherent superposition of two squeezed coherent states that share the same displacement-and develop an analytical framework, based on a family of Generalized Squeezing Polynomials, that yields closed-form expressions for arbitrary-order factorial moments and coherence functions $g^{(k)}(0)$, the full Wigner function, and the quantum Fisher information. The analysis shows how interference at a fixed mean, driven by a mismatch of the component covariances rather than by mean separation, can be precisely engineered to transform the extreme photon bunching of the constituents into strong sub-Poissonian and even perfect multiphoton suppression. We further provide a rigorous quantum Fisher information analysis, proving that parameters encoded by linear generators (for example, the number operator) are bounded by the standard quantum limit, whereas parameters encoded by quadratic generators (for example, squeezing transformations) achieve Heisenberg-limited scaling. Together, these results furnish a complete analytical toolkit for a versatile class of non-Gaussian states, establishing the displaced Janus state as a key primitive for hybrid quantum protocols, quantum metrology, and fault-tolerant continuous-variable computation.

quant-ph↗

arXiv2025

N-Photon Emission from Uniform Acceleration

We present a generalized framework for $n$-photon processes involving a uniformly accelerated Unruh-DeWitt detector interacting with a massless scalar field. We utilize the $n^\text{th}$ order Dyson series to derive the final quantum state for an arbitrary number of interactions. Our analysis covers both even-order processes, which return the detector to its initial state, and odd-order processes, which result in a change of the detector's state. By employing a unified formalism and performing a complete, time-ordered integration, we obtain exact analytical expressions for the $n$-photon states. The results reveal a rich structure of resonant denominators corresponding to multi-particle processes, including new field-mediated resonances independent of the detector's energy gap for $n>2$. Crucially, the analysis of odd-order transitions reveals an exponential factor, $\exp(-\pi\omega/a)$, characteristic of the Unruh thermal bath. By considering processes starting from the detector's excited state, we demonstrate that the ratio of excitation to de-excitation amplitudes precisely recovers the Boltzmann factor, providing a higher-order confirmation of thermal detailed balance for the Unruh effect. This work provides a unified tool for studying multipartite entanglement and thermal phenomena in non-inertial frames.

hep-th↗

arXiv2025

Two-photon emission from uniform acceleration: Unruh excitation, radiative decay, and field entanglement

We analyze the two-photon emission process of a uniformly accelerated Unruh-DeWitt detector interacting with a massless scalar field in Minkowski spacetime. Using second-order perturbation theory, we derive the exact final quantum state of the field and classify the emitted photon pairs according to their directional decomposition into Unruh modes: right-right (RR), left-left (LL), and mixed (RL/LR) channels. The RR and LL contributions produce photon pairs within a single Rindler wedge, while RL and LR emissions generate entanglement across wedges. The first emission arises from a counter-rotating (Unruh) excitation, followed by a rotating Wigner-Weisskopf-like decay. Our results reveal how acceleration imprints entanglement and thermal structure on the radiation, offering new insight into quantum field theory in non-inertial frames and potential applications in relativistic quantum information.

hep-th↗

arXiv2025

Vacuum-Induced Quantum Gate

We demonstrate that the quantum vacuum, as perceived by a uniformly accelerating observer, can be harnessed to perform a quantum Z-gate. A two-level Unruh-DeWitt detector, prepared in a superposition of its ground and excited states, undergoes a second-order interaction with the vacuum, resulting in a two-photon emission. We derive the exact analytical form of the final entangled detector-field state and show that this emission is conditional on a phase flip of the detector's initial state-the defining feature of the gate's operation. This process harvests entanglement from the Minkowski vacuum, producing photon pairs entangled across causally disconnected Rindler wedges. This work reframes acceleration-induced radiation not as thermal noise but as a coherent computational resource, offering new pathways for relativistic quantum information.

quant-ph↗

arXiv2025

Quantum Complementarity ad Infinitum: Switching Higher-Order Coherence from Infinity to Zero

We report a profound manifestation of quantum complementarity in the higher-order photon statistics of the ``Janus state,'' a coherent superposition of two squeezed vacua. We find that the state acts as a perfect quantum switch for multi-photon correlations, toggled by the availability of which-path information. Erasing this information activates quantum interference that can be tuned to be maximally destructive. This reveals a remarkable hierarchy of suppression: while two-photon correlations remain finite, we prove analytically and demonstrate numerically that it is possible to drive all higher-order correlations ($g^{(k)}$ for $k \ge 3$) to zero. This transition from the extreme bunching of the constituent states ($g^{(k)} \to \infty$) to a state of profound quantum order is visualized by the emergence of negativity in the state's Wigner function, an unambiguous signature of non-classicality. This work provides a foundational demonstration of quantum complementarity in multi-photon statistics and introduces a new paradigm for engineering highly ordered, non-classical light from Gaussian resources.

quant-ph↗

arXiv2025

Kappa Plane Wave Modes and Continuous Squeezing in Quantum Field Theory

We introduce a new family of field modes in flat spacetime -- termed $\kappa$-plane wave modes -- constructed from $\kappa$-dependent linear combinations of Minkowski plane waves. These modes define a one-parameter family of vacua, $|0_\kappa\rangle$, that smoothly interpolate between different quantizations, reducing to the Minkowski vacuum in the limit $\kappa \to 0$. We show that $|0_\kappa\rangle$ is uniquely characterized as a continuous-mode squeezed vacuum, with frequency-dependent squeezing parameter $r(\nu)$ satisfying $\tanh r(\nu) = e^{-\pi \nu/\kappa}$. We also derive two Bogoliubov transformations between $\kappa$-plane wave and $\kappa$-Rindler operators, which exhibit a universal form and smoothly interpolate between all known mode decompositions, including those of Minkowski, Rindler, and Unruh quantizations as limiting cases.

hep-th↗

arXiv2025

Hodge Duals in Spherical Compactifications

We present a general formalism for computing the Hodge dual of differential forms in arbitrary dimensions subject to a spherical constraint. This problem arises naturally in Kaluza-Klein compactifications, where sphere reductions demand careful treatment of differential forms constrained to lie on embedded submanifolds. We derive an explicit expression for the Hodge dual of a $p$-form in the presence of such constraints and validate our general ansatz through illustrative examples in three dimensions, including both flat and diagonal metric backgrounds. The resulting framework offers a systematic and practical tool for handling constrained Hodge duals, with direct applications to consistent truncations in supergravity and string theory compactifications.

hep-th↗

arXiv2025

Phase-Induced Particle Creation in the Kappa-Gamma Vacuum

We develop a two-parameter family of flat-spacetime modes labeled by a deformation scale $\kappa$ and a phase angle $\gamma$, extending the $\kappa$-plane wave framework to include complex squeezing. The resulting $\kappa\gamma$ basis provides a globally well-defined mode decomposition whose associated vacuum $|0_{\kappa,\gamma}\rangle$ is a continuous-mode phase-squeezed state: $\kappa$ fixes the squeezing magnitude, while $\gamma$ sets the squeezing angle in phase space. We identify phase-induced particle creation, in which a relative phase mismatch $\Delta\gamma$ between observers generates a nontrivial particle spectrum governed by $(\kappa,\Delta\gamma)$ even when $\kappa$ is held fixed. We then derive the two reciprocal Bogoliubov maps: the $\kappa\gamma$ plane-wave operators in terms of $\kappa'$-Rindler operators, and conversely the $\kappa'$-Rindler operators in terms of $\kappa\gamma$ plane-wave operators, providing a closed algebraic bridge between these bases. Finally, by analyzing the Wightman function we show that $|0_{\kappa,\gamma}\rangle$ is globally regular, with no singularities beyond those of the standard Minkowski vacuum.

hep-th↗

arXiv2025

A Tunable Unruh Effect: Accelerated Detectors in Kappa-Rindler Vacua

We study the response of an accelerated Unruh-DeWitt detector to a one-parameter family of ``kappa Rindler'' vacua, which generalize the standard Unruh effect. These states, parameterized by $\kappa$, continuously interpolate between the Rindler ($\kappa \to 0$) and Minkowski ($\kappa=1$) vacua. We find the detector registers a perfect thermal bath at a tunable temperature $T_\kappa = \kappa T_U$. This result establishes a framework for environments perceived as both ``hotter'' ($\kappa>1$) and ``colder'' ($\kappa<1$) than the standard Unruh temperature. We establish this thermality by demonstrating the KMS condition for the Wightman function and by analyzing the associated particle creation process. Furthermore, we visualize the spacetime structure of the created field quanta, revealing an intuitive link between the $\kappa$-controlled symmetry of the modes and the perceived temperature. Our work provides a comprehensive framework for a modulated Unruh effect, bridging formal QFT with clear visual intuition.

hep-th↗

arXiv2025

The Janus State: A Universal Lower Bound for Second-Order Coherence

A single-mode squeezed vacuum is a foundational quantum state that, despite its nonclassical nature, exhibits classical-like, super-Poissonian photon statistics. This feature motivates a ``quantum-of-quantum'' inquiry: can the superposition of two such states generate the opposite behavior -- strongly sub-Poissonian light? We demonstrate that the ``Janus state,'' a coherent superposition of two squeezed vacua with opposing orientations, achieves precisely this. Our exact analytic solution reveals a universal lower bound on second-order coherence, showing that $g^{(2)}$ cannot be driven below 1/2. The mechanism is tuned interference that suppresses two-photon events. Beyond this asymptotic bound, we identify a practical minimum of $g^{(2)} \approx 0.567$ at moderate squeezing, defining an accessible ``sweet spot.'' While requiring a minimal non-Gaussian element for its creation, the Janus state establishes a definitive performance limit for engineering sub-Poissonian photon statistics from Gaussian resources, with a clear path toward quantum applications.

quant-ph↗