All You Need is Amplifier: Spectral Imposters Without Pulse Shaping

Abstract

Quantum tracking control encodes the desired dynamics into a tailored driving field; here, we let the system find its own way there. We propose a real-time feedback control framework in which a proportional controller continuously corrects a simple transform-limited field based on the instantaneous mismatch between two systems' responses - producing the required control on the fly, without prior waveform design. The framework is demonstrated on two distinct examples: a single-active-electron atom, where hydrogen is driven to mimic argon's strong-field optical emission, and a Fermi-Hubbard chain, where a weakly interacting lattice reproduces the transport dynamics of a Mott-insulating reference. By shifting the control paradigm from predesigned inputs to adaptive response tracking, this approach establishes closed-loop feedback as a broadly applicable route to programmable quantum dynamics.

Figures (3)

• Figure 1: Driven imposters via optical feedback. A? proportional controller feeds back the optical response of the driven system until the generated field reproduces the response of the reference system.
• Figure 2: Time-domain high-harmonic response $d\langle \hat{p}\rangle/dt$ for argon (reference, blue) and hydrogen (driven, orange) within the single-active-electron model. (a) Without feedback: the two atoms exhibit distinct nonlinear responses under identical transform-limited driving $E_{\rm tl}(t)$. (b) With amplification gain $k_p=1000$: the hydrogen response converges to the argon reference signal, demonstrating dynamical tracking and optical mimicry.
• Figure 3: Many-body current tracking in the one-dimensional Fermi--Hubbard model ($L=10$, half filling), $U_{\rm ref}/t_0=10$ and $U_{\rm dr}/t_0=1$. (a) Without feedback, the time derivative of the current expectation value differs significantly in amplitude and phase. (b) With amplifier gain $k_p=1000$, the driven system reproduces the reference response, $\frac{d}{dt}\langle \hat{J} \rangle_{\rm dr} \to \frac{d}{dt}\langle \hat{J} \rangle_{\rm ref}$.