arXiv subjects

Miao-Miao Yi

Publications and source records attributed to Miao-Miao Yi.

6 recordsLinked to original sources

arXiv2026

Reliability-Safety Trade-off in AI Distillation: A Renormalization-Group Approach

Knowledge distillation transfers more than task competence: it also transmits response propensities, refusal policies, error boundaries, and latent safety biases. We formulate this behavioral inheritance as a coarse-graining model grounded in statistical mechanics, in which the student's answer and refusal decisions define two macrostates, while the teacher induces an effective field that reshapes the student's free-energy landscape. The model yields a reliability-safety trade-off relation controlled by a single parameter K, which we term the hazard discrimination capability. The predicted trade-off is consistent with refusal-token data [arXiv: 2412.06748]. In knowledge distillation, a teacher with strong hazard discrimination improves the student's attainable reliability and safety, whereas poor discrimination limits the attainable trade-off. Repeated distillation acts as an iterated renormalization-group-like transformation, under which K follows a flow across generations. The flow exhibits a tricritical structure separating regimes of K loss, stable transmission, and threshold-dependent inheritance, and yields testable scaling predictions for multigenerational distillation.

cond-mat.stat-mech↗

arXiv2026

Wave packet landscape in open quantum systems

We formulate a landscape theory for the long-time wave packet spreading of free and harmonically trapped particles with quantum fluctuations and its related dissipation. We show that the diffusion, localization, and collapse of wave packets arise from symmetry structures of an underlying landscape in covariance space. The geometry of this landscape determines the asymptotic fate of the wave packet. In the quantum landscape description, the trapping potential and bath fluctuation break the landscape symmetry in distinct ways: the former lifts the valley-like landscape of a fluctuation-free free particle into a bowl-like landscape, leading to collapse, whereas the latter tilts the valley and turns localization into diffusion. The resulting landscape symmetry breaking accounts for the noncommuting long-time limits and abrupt changes in the asymptotic wave-packet width. This establishes landscape symmetry breaking as a unified geometric origin of wave-packet diffusion, localization, and collapse in quantum Brownian motion.

quant-ph↗

arXiv2026

Capacity-time Trade-off in Highly Reliable Quantum Memory

Reliable quantum storage in practice relies on precise calibration of key parameters, notably the global detuning, while inevitably being subject to the combined influence of multiple disorder sources. In this work, a comprehensive model for an Electromagnetically induced transparency (EIT) protocol is considered, in which coupling disorder and detuning disorder are incorporated simultaneously. After quantitatively analyzing the control dynamics, a highly precise phase-detuning relation to improve calibration accuracy is obtained. Building on this result, a Berry-phase-based control strategy is proposed to mitigate the degradation caused by the global detuning. We further reveal that there exists a joint effect simultaneously induced by different disorder sources, which can substantially reshape the decoherence. Finally, an effective notion of storage capacity is introduced and a general time-capacity relation is obtained, providing guidance for subsequent experimental optimization and device design.

quant-ph↗

arXiv2026

Third Quantization for Order Parameters (II): Local Field Quantization in Superconducting Quantum Circuits

The quantization of superconducting transmission-line resonators is usually introduced phenomenologically by modeling the resonator as an effective LC circuit and imposing canonical commutation relations on macroscopic variables such as charge and flux. Although this approach is highly successful, it leaves open why these macroscopic variables should obey quantum commutation relations and how this behavior emerges from the superconducting state. In this work, starting from the microscopic pairing Hamiltonian underlying BCS superconductivity, we derive the low-energy effective Hamiltonian of a circuit-QED architecture containing a superconducting transmission line with distributed capacitive and inductive elements. We establish quantitative relations between macroscopic observables, including current and voltage, and the spatially local superconducting phase, as well as the microscopic parameters of the electron-phonon system. We then extend the third quantization of the superconducting order parameter, introduced in Paper (I) for the global phase, to the spatially local case. This gives a macroscopic field quantization of the superconducting phase. We show that, after restriction to the low-energy excitation subspace, the local superconducting phase becomes a genuine quantum dynamical variable. Thus, the quantum behavior of transmission-line resonators need not be postulated at the macroscopic level, but follows from the third quantization of the superconducting order parameter. These results suggest that capacitive and inductive superconducting circuit elements share the same microscopic origin, providing a unified framework for superconducting circuit quantization.

quant-ph↗

arXiv2026

The effect of investor-driven information diffusion on excess comovement: Evidence from retail and institutional investors in China and the United States

This study investigates how cross-stock information diffusion, driven by both retail and institutional investors, influences excess comovement in the Chinese retail-dominated market and the U.S. institution-dominated market. Using data from 4,533 Chinese stocks and 4,517 U.S. stocks from 2010 to 2022, we identify three key findings. First, the dominant investor group in each market significantly drives excess comovement. Specifically, in China, compared with institution-driven diffusion, retail-driven information diffusion has a notably stronger effect on excess comovement. In contrast, in the U.S., institution-driven diffusion is the primary driver of excess comovement, surpassing the influence of retail-driven diffusion. Second, we identify investors' trading behavior as the underlying mechanism through which information diffusion affects excess comovement. Third, we observe a lead-lag relationship: stocks with faster retail-driven information diffusion exhibit comovement that precedes those with slower diffusion. Based on this finding, we further demonstrate that the predictive power of information diffusion varies across markets. In China, retail-driven diffusion shows strong and persistent predictability for excess comovement, whereas in the U.S., institution-driven diffusion exhibits similarly robust predictive capacity.

q-fin.GN↗

arXiv2026

Third Quantization for Order Parameter (I): BCS-BEC crossover with macroscopically coherent state

We revisit the quantization of the order parameter, which we refer to as third quantization, from the perspective of the commutation relation between the phase operator of the order parameter and the particle-number operator. We show that this macroscopic commutation relation does not constitute an independent fundamental postulate added to quantum mechanics, but instead emerges naturally from second quantization in the thermodynamic limit for both bosonic and fermionic many-body systems. In this sense, both Bose-Einstein condensates (BECs) and Bardeen-Cooper-Schrieffer (BCS) states can be understood as macroscopic quantum states described by bosonic coherent states: in BEC, bosons condense into a single coherent mode with a well-defined phase, while in BCS systems, collective excitations of Cooper pairs can also acquire an effectively bosonic coherent description. On this basis, we propose a new macroscopic interpretation of the BCS-BEC crossover. To characterize this crossover, we model a conventional superconductor as an assembly of macroscopically separated superconducting segments. As the intra-segment coupling increases, the system evolves from a BCS-like regime toward a BEC-like regime, in which the segments collectively behave as macroscopic coherent states. Inter-segment tunneling then locks their phases, establishes global phase coherence, and gives rise to a bulk Bose-Einstein condensate. The phase diagram of the BCS-BEC crossover can thus be understood as a manifestation of a macroscopic quantum process governed by the coherent-state dynamics of the order parameter. Our results provide a unified perspective on BEC, BCS superconductivity, and the BCS-BEC crossover within the framework of third quantization.

quant-ph↗