Paper I established a single-atom baseline for room-temperature Rydberg electromagnetically induced transparency (EIT) in thermal rubidium vapor and reported two unresolved numerical questions: whether genuine counter-intuitive pulse ordering improves Stark-chirped rapid adiabatic passage (SCRAP)-assisted transfer, and whether Fibonacci-modulated control improves coherence beyond merely broadening the drive spectrum. We address both directly. Using the same three- level ladder Hamiltonian, decay rates, and 10 ns pulse window as the prior preprint, we find that counter-intuitive ordering within the fixed window degrades transfer efficiency to near zero (0.02%) rather than improving it, and we diagnose the failure as a short-window boundary-condition problem rather than a failure of the STIRAP mechanism itself. We then model a stored |1⟩–|3⟩coherence subject to Ornstein–Uhlenbeck dephasing noise and compare periodic and Fibonacci-timed π-phase- flip sequences using direct time-domain Monte Carlo simulation. In the regime where the noise correlation time matches the inter-pulse spacing, Fibonacci timing yields a 2.4×coherence advantage over periodic decoupling (0.0266 vs. 0.0110), while periodic decoupling outperforms Fibonacci in the quasi-static noise limit (0.964 vs. 0.785). We report both the negative and positive results transparently, without tuning parameters to force a preferred outcome.
Paper I established a single-atom baseline for room-temperature Rydberg electromagnetically induced transparency (EIT) in thermal rubidium vapor and reported two unresolved numerical questions: whether genuine counter-intuitive pulse ordering improves Stark-chirped rapid adiabatic passage (SCRAP)-assisted transfer, and whether Fibonacci-modulated control improves coherence beyond merely broadening the drive spectrum. We address both directly. Using the same three- level ladder Hamiltonian, decay rates, and 10 ns pulse window as the prior preprint, we find that counter-intuitive ordering within the fixed window degrades transfer efficiency to near zero (0.02%) rather than improving it, and we diagnose the failure as a short-window boundary-condition problem rather than a failure of the STIRAP mechanism itself. We then model a stored |1⟩–|3⟩coherence subject to Ornstein–Uhlenbeck dephasing noise and compare periodic and Fibonacci-timed π-phase- flip sequences using direct time-domain Monte Carlo simulation. In the regime where the noise correlation time matches the inter-pulse spacing, Fibonacci timing yields a 2.4×coherence advantage over periodic decoupling (0.0266 vs. 0.0110), while periodic decoupling outperforms Fibonacci in the quasi-static noise limit (0.964 vs. 0.785). We report both the negative and positive results transparently, without tuning parameters to force a preferred outcome.
Deterministic quantum state control at ambient temperature remains a central challenge for scalable photonic quantum technologies. Thermal rubidium vapor cells offer a cryogenic-free platform for light-matter interaction, but Doppler broadening, collision-induced dephasing, and transit-time effects limit coherent state transfer. We present a CMOS-compatible photonic architecture for studying room-temperature Rydberg electromagnetically induced transparency (EIT) in rubidium vapor, combining integrated on-chip pulse generation, counter-propagating beam geometry, and Stark-Chirped Rapid Adiabatic Passage (SCRAP). The platform integrates an on-chip silicon nitride pulse-generation stage, dual-wavelength optical addressing at 780 nm and 480 nm, a heated rubidium vapor microcell near 140°C, and a quasiperiodic Fibonacci control layer. We model the atomic response with a three-level ladder Hamiltonian and confirm numerically that the EIT transparency window scales as Ωc²/Γe, consistent with analytic theory. Thermal averaging over the Maxwell-Boltzmann velocity distribution confirms that counter-propagating excitation reduces residual Doppler-induced absorption relative to a co-propagating geometry. Fibonacci-modulated control fields are shown to possess substantially broader spectral content than periodic modulation, supporting their use as a candidate noise-avoidance strategy; this is presented as a spectral-shaping hypothesis, not as established topological protection. Numerical scans of SCRAP-assisted Rydberg transfer under realistic Rabi frequencies do not yet show a clear efficiency advantage over resonant excitation, and this is reported as an open problem for parameter optimization. We do not claim a demonstrated two-qubit logic gate; multi-atom blockade dynamics and gate fidelity benchmarking are identified explicitly as future work.
A downstream memory cannot freeze, replay, or increase the information content of a high-energy collision after detector transduction. We prove this claim using contractivity of trace distance under completely positive trace-preserving maps: once two collision states have become indistinguishable in the detector record, no later optical buffer can restore their distinguishability. The scientifically admissible question is therefore narrower: can an alreadytransduced, bandwidth-matched optical pulse be stored and retrieved more effectively in a periodic, quasiperiodic, or explicitly driven memory medium under controlled disturbances? We formulate a preregisterable bench-scale benchmark with matched optical depth, input spectrum, control power, and disturbance history. The memory is treated as an open quantum channel governed by Maxwell–Bloch or Lindblad dynamics; performance is assessed by retrieval efficiency, waveform or state fidelity, added noise, storage time, bandwidth, and time-bandwidth product. We distinguish quasiperiodic localization from topological protection and prove a Floquet no-go: for a single scalar cosine drive, the leading van Vleck commutator vanishes, so a first-order Floquet gap cannot be inferred. A nonzero first-order correction requires at least two noncommuting drive quadratures. A reproducible nine-site single-excitation design study compares periodic, quasiperiodic, and matched-random detuning patterns under equal loss and dephasing. For the predeclared normalized integrated return probability over 0 ≤ t ≤ 20J−1, the uniform baseline is 0.247. The best scanned median values are 0.379 for periodic modulation, 0.391 for quasiperiodic modulation, and 0.384 for a matched-random null. Their replicate intervals overlap strongly. The toy model therefore shows that static modulation can suppress coherent leakage in some regimes, but it does not establish quasiperiodic specificity, topological protection, an LHC advantage, or a quantum-memory implementation. The admissible near-term result is a blinded comparative bench test, not “frozen collision dynamics” and not an LHC detector upgrade. Frozen claim boundary. This manuscript does not claim that a quantum buffer stores the original collision state; that delayed readout increases detector time resolution; that an Aubry–André potential is automatically topological; that localization necessarily improves coherence; that a scalar Floquet drive opens a leading-order gap; that NV centres are qualified for an LHC radiation environment; or that the synthetic design study predicts laboratory performance. It establishes no-go results, a controlled open-system benchmark, and a matched-null simulation that defines what must be demonstrated before stronger claims are admissible.
We investigate collective chirped stimulated Raman adiabatic passage (STIRAP) in a pair of identical three-level atoms using a symmetric six-state model. Numerical simulations reveal a pronounced oscillatory dependence of the population transfer to the doubly excited Rydberg state on the peak Rabi frequency, indicating dynamics beyond the conventional single-dark-state description of STIRAP. To identify the underlying mechanism, we develop a dressed-manifold description based on gauge-invariant projections onto nearly degenerate instantaneous dressed manifolds. The analysis demonstrates that the wavefunction remains predominantly confined to a two-dimensional dark manifold while becoming transiently coupled to a neighboring bright manifold during the pulse-overlap interval. We further show that in the dressed-manifold representation, the Rydberg-Rydberg interaction modifies the collective resonance structure while preserving the dark-bright manifold dynamics responsible for the oscillatory transfer; an appropriately chosen frequency chirp compensates the interaction-induced detuning and restores efficient population transfer. This dressed-manifold picture provides a consistent interpretation of oscillatory collective transfer and establishes a framework for controlling adiabatic dynamics in interacting multilevel systems by linearly chirped STIRAP, opening a route toward manifold-based control of Rydberg-mediated quantum gates, correlated-state preparation, and other coherent operations in interacting atomic systems.
The transient dynamics of electromagnetically induced transparency (EIT) are fundamental to understanding coherent light–atom interactions and the advancement of quantum technologies such as optical switching and quantum memory. However, in room-temperature atomic vapors, Doppler broadening significantly alters these dynamics, yet a comprehensive understanding of its impact on the transient EIT response remains lacking. In this study, we combine analytical and numerical methods to investigate the absorption dynamics of a weak probe field in a three-level Λ-type system driven by a strong coupling field, based on the optical Bloch equations and Laplace transform techniques. Our results show that the transient response is highly sensitive to both the atomic spontaneous emission rate and the Rabi frequency of the coupling field. Increasing the coupling field intensity not only accelerates the approach to steady state but also induces oscillatory dynamics and negative absorption. Under Doppler broadening, the time required to reach steady state increases by approximately three orders of magnitude compared to the Doppler-free case—an effect that is surprisingly insensitive to temperature variations across the 100–400 K range. Moreover, restoring a short steady-state time under broadened conditions necessitates increasing the coupling laser intensity by two orders of magnitude. These findings provide key insights into the influence of Doppler broadening on coherent transient processes and offer practical guidelines for the design of room-temperature atomic devices, including quantum memories and optical modulators.
The scalability of Noisy Intermediate-Scale Quantum (NISQ) devices is currently constrained by material defects, specifically Two-Level Systems (TLS) that induce resonant decoherence in superconducting qubits. This study presents a comprehensive experimental analysis using the IBM Quantum ibm_fez processor to demonstrate "Software-Defined Hardware" optimization. By employing a novel "Instruction-Level Calibration Injection" technique, we bypass standard compiler constraints to inject continuous off-resonant AC Stark drives (Nshots=4096). Methodology The experiment utilizes a Floquet engineering approach to perform pulse-level Hamiltonian engineering. We implement custom instruction-level calibrations to apply continuous off-resonant AC Stark drives, effectively modifying the qubit frequency to avoid resonant interactions with defect states. Key Findings The application of this protocol yielded three primary results: Spectral Decoupling: Successfully restored Ramsey fringes in a defect-limited qubit (Q150), achieving a coherence time of T2∗≈6.36μs. Protocol Benchmarking: The "Stark Rescue" protocol demonstrated a statistical advantage over standard CPMG dynamical decoupling. It extended coherence time by 11.3% (T2Stark=8.17μs vs. T2CPMG=7.34μs; p=0.042, Bootstrap t-test). Topological Simulation: Digital simulation of a topological domain wall under engineered correlated noise revealed a sigmoidal stability threshold (SSE≈0.0008), significantly outperforming standard exponential models (SSE≈0.0085). Conclusion These results confirm that pulse-level Hamiltonian engineering can effectively reclaim compromised hardware resources on current NISQ platforms. Keywords NISQ, Superconducting Qubits, Two-Level Systems (TLS), Floquet Engineering, AC Stark Effect, IBM Quantum, Dynamical Decoupling, Quantum Control.
Abstract Dynamical decoupling (DD) is a quantum error-mitigation technique based on applying sequences of control pulses to suppress decoherence. Here we perform a numerical study to compare different DD protocols, namely Carr-Purcell-Meiboom-Gill (CPMG), Periodic Dynamical Decoupling (PDD), Concatenated Dynamical Decoupling (CDD) and Uhrig Dynamical Decoupling (UDD) applied to three commonly used noise power spectral densities: (i) white, (ii) 1/f, (iii) 1/f 2 and their hybrid combinations. By ignoring qubit relaxation, we simulate these protocols focusing purely on dephasing noise. We then consider independent multi-axial noise with uniaxial control pulses. The effective coherence times T2,eff are extracted for each case and compared with the baseline free induction decay T ∗ 2 [6]. In all these simulations, the time-domain decoherence profiles follow a stretched exponential form ∼ exp −(t/T2,eff) β with the effective coherence times dependent on the noise spectrum considered, the strength of the noise, and the DD sequence employed. An exception is observed for the UDD under specific noise conditions where it cannot be described by a simple stretched exponential decay form.