The study investigates memory and transport processes in open quantum systems. A straightforward replacement of bath occupations while maintaining arbitrary system, bath coherences does not guarantee a physically realizable fermionic state. Instead, researchers construct a two-reservoir protocol utilising independent, number-conserving thermal attenuators which ensures complete positivity and fermionic admissibility by design. Physical attenuation inherently alters both bath populations and cross correlations; coherence control is therefore not an independently adjustable parameter. Furthermore, quadratic dynamics simplifies the stroboscopic problem to an exact matrix fixed-point equation without relying on weak-coupling or Markov approximations. Analytical results are presented.

Two-Reservoir Protocol Enables Realistic Quantum State Resetting and Enhanced Coherence Transfer

Retained one-body coherence, a measure of quantum memory, enhances short-cycle transfer rates exceeding those previously achievable in fermionic systems; specifically, nonzero particle transport occurs even at complete erasure when it maximizes coherence retention. Prior methods failed to produce physically realistic states because they couldn’t simultaneously adjust both system and reservoir populations alongside coherences during environmental renewal. The two-reservoir protocol utilizes number-conserving thermal attenuators to ensure complete positivity and physical admissibility by design, accurately modelling real quantum behaviour and overcoming limitations that prevented viable reset operations.

Calculations using finite open chains revealed non-zero particle transfer even with full initial coherence loss if maximal coherence retention maintains a minimal setting for observing this effect. This achievement stems from the use of number-conserving thermal attenuators which modify bath populations *and* cross correlations between them; controlling coherence isn’t independent of adjusting these population levels. Furthermore, a nonzero short-cycle transfer kernel persists below unity retention, establishing distinct operating points for retained one-body coherence, throughput, and energy flow in biased structured reservoirs.

Residual Particle Transfer Limits Complete Reset Fidelity

The two-reservoir protocol offers physically realistic coherence control within quadratic dynamics, sidestepping issues that plagued earlier environmental renewal attempts, but it doesn’t resolve all challenges surrounding complete erasure of inter-cycle memory. No general theorem guarantees suppression of particle transfer even when coherence is fully erased, raising a key tension between achieving truly independent “hard” resets versus accepting unavoidable residual transport during reset cycles.

Despite acknowledging the impossibility of guaranteeing full elimination of particle transfer during resets, these findings remain important; this work establishes an essential benchmark for understanding how reservoir coherence affects both particle movement and energetic exchange.

An exactly solvable framework studies quantum dynamics without relying on approximations often used in similar calculations thanks to the two-reservoir protocol. Preservation of quantum information alongside environmental renewal within complex systems is now possible through a physically admissible control method, a significant step beyond earlier attempts hampered by unrealistic state generation during reset operations. Adjustments to bath populations *and* correlations are crucial when manipulating coherence levels using a two-reservoir system governed by number-conserving thermal attenuators, revealing that these parameters aren’t independently controllable. Future research will likely explore extending this approach to more complex systems, potentially unlocking new control methods.

This research demonstrated a physically realistic way to preserve quantum information while renewing the environment surrounding a quantum system, utilizing a two-reservoir protocol with number-conserving thermal attenuators within quadratic dynamics. The study revealed that controlling coherence requires simultaneous adjustments to both population levels and correlations in the reservoirs, coherence is not an independent setting.

Results show particle transfer can persist even when attempting complete erasure of memory, establishing distinct operating points for coherence retention, throughput, and energy flow in biased structured reservoirs; no general theorem prevents such transport during reset cycles. This work provides a benchmark for understanding how reservoir properties influence quantum control methods.

👉 More information
🗞 Memory–Transport Competition in Physical Two-Bath Quantum Reset Dynamics
✍️ Jishad Kumar and Tapio Ala-Nissila (Aalto University); Achilleas Lazarides (Loughborough University)
🧠 ArXiv: https://arxiv.org/abs/2610.30457

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