Asymptotic Scaling of Precision Limits in Continuous Gaussian Quantum Metrology

• Kazuki Yokomizo (University of Tokyo)

Room: 5F Seminar Room Continuous quantum metrology holds promise for achieving high-precision sensing by harnessing information progressively carried away by radiation quanta emitted into the environment. Despite recent progress, a comprehensive understanding of the fundamental precision limits of continuous metrology with bosonic systems is still lacking. In this work, we develop a general theoretical framework for quantum metrology with multimode free bosons under continuous Gaussian measurements. Within this framework, we derive analytical expressions for the asymptotic growth rates of the global quantum Fisher information (QFI) and the environmental QFI, which quantify the total information encoded in the joint system-environment state and the information accessible from the emitted radiation, respectively. We then derive scalings and bounds for these quantities, showing that while a quadratic scaling with the number of modes is attainable, the precision scales at most linearly with time and a meaningful energy resource.

Effective Hamiltonian approach for monitored Majorana chains

• Yohei Fuji (Ritsumeikan University)

Room: 5F Seminar Room Many-body quantum systems under monitoring of local observables provide a new platform for exploring nonequilibrium phenomena, such as measurement-induced phase transitions and unconventional entanglement phases. In this talk, we introduce an effective Hamiltonian framework for these systems. Taking a monitored version of the Kitaev-Majorana chain as an example, we show that its topological area-law entangled phase exhibits a bulk-edge correspondence in the effective Hamiltonian. We also show that its subvolume-law entangled phase corresponds to the gapless phase of an effective Hamiltonian with correlated long-range hoppings. The effective Hamiltonian thus provides a bridge between monitored dynamics and ground-state physics.

Role of quantum metric in nonlinear transport

• Sota Kitamura (Kyoto University)

Room: P7A Seminar Room Quantum geometry plays an important role in a variety of transport phenomena in crystalline solids. While its effects on transverse transport have been extensively studied, its role in longitudinal transport remains less well understood. In particular, different theoretical approaches to nonlinear DC transport have led to seemingly conflicting results, raising questions about the underlying physical mechanisms. In this seminar, I present a microscopic framework for nonlinear transport based on adiabatic time evolution and show how the quantum metric gives rise to a nonreciprocal current through a quantum correction to the electronic distribution function. Our results highlight the importance of a microscopic treatment of dissipation, beyond the phenomenological prescriptions commonly employed in nonlinear transport theory.