arXiv subjects

Tsai-Chen Lee

Publications and source records attributed to Tsai-Chen Lee.

7 recordsLinked to original sources

arXiv2026

Rapid Cavity-Based Mid-Circuit Measurement and Feedforward in a Neutral Atom Array

Measuring part of a quantum system in the midst of its evolution and acting on the result in real time is essential for numerous quantum information protocols. Neutral-atom arrays are a leading platform for quantum information processing, but their mid-circuit measurement-and-feedforward cycle times have remained slow, typically exceeding 1 ms. Here we demonstrate fast mid-circuit measurement and real-time feedforward in an array of atomic qubits coupled to a high-finesse optical cavity. Local light shifts tune individual data qubits out of resonance with the cavity, shielding their coherence, while a near-resonant probe drives a selected qubit whose emission is collected with Purcell enhancement. Mid-circuit measurements of four qubits with sub percent infidelity reduce the coherence of a fifth unmeasured data qubit by less than 2%. We implement real-time feedforward to correct measurement-induced phase shifts and to realize an adaptive circuit for optimal quantum state discrimination and conditional state preparation. Our approach reduces the measurement-and-feedforward cycle time to below 100 $μ$s and establishes optical cavities as a route to fast control of neutral-atom quantum systems.

quant-ph↗

arXiv2026

Astigmatism-free 3D Optical Tweezer Control for Rapid Atom Rearrangement

Reconfigurable neutral-atom arrays are a promising platform for quantum computing, quantum simulation, and quantum metrology, but atom transport using frequency-chirped acousto-optic deflectors (AODs) is limited by chirp-induced acoustic lensing and trajectory distortion. We address these limitations using a three-dimensional acousto-optic deflector lens (3D-AODL), a design predicted to reduce long-range transport times by more than a factor of two. We further introduce fading-Shepard waveforms that circumvent finite AOD bandwidth, enabling sustained axial displacement. We demonstrate unrestricted three-dimensional optical-tweezer motion over a 200 $μ$m $\times$ 200 $μ$m $\times$ 136 $μ$m volume with velocities exceeding 4.2 m/s. Arbitrary three-dimensional control of optical-tweezer trajectories enables rapid atom rearrangement and dynamical engineering of optical potentials in tweezer arrays and optical lattices. This capability advances quantum control and atom manipulation in neutral-atom quantum processors by enabling faster rearrangement, higher clock rates, and scalable sorting in complex geometries.

physics.optics↗

arXiv2026

Higher symmetry breaking and non-reciprocity in a driven-dissipative Dicke model

Higher symmetries in interacting many-body systems often give rise to new phases and unexpected dynamical behavior. Here, we theoretically investigate a variant of the Dicke model with higher-order discrete symmetry, resulting from complex-valued coupling coefficients between quantum emitters and a bosonic mode. We propose a driven-dissipative realization of this model focusing on optomechanical response of a driven atom tweezer array comprised of $n$ sub-ensembles and placed within an optical cavity, with the phase of the driving field advancing stepwise between sub-ensembles. Examining stationary points and their dynamical stability, we identify a phase diagram for $n\geq 3$ with three distinctive features: a $\mathbb{Z}_n$ ($\mathbb{Z}_{2n}$) symmetry-breaking superradiant phase for even (odd) $n$, a normal unbroken-symmetry phase that is dynamically unstable due to non-reciprocal forces between emitters, and a first-order phase transition separating these phases. This $n$-phase Dicke model may be equivalently realized in a variety of optomechanical or opto-magnonic settings, where it can serve as a testbed for studying high-order symmetry breaking and non-reciprocal interactions in open systems.

quant-ph↗

arXiv2026

Autler-Townes spectroscopy of a Rydberg ladder

Ladder-type two-photon excitation of an atom from a ground state $|g\rangle$, to an intermediate excited state $|e\rangle$, and, finally, to a Rydberg state $|r\rangle$, has a variety of uses from quantum information to sensing. A common scheme for detecting this transition optically is through electromagnetically induced transparency (EIT). However, in inverted wavelength schemes, where the ground-to-excited transition wavelength is shorter than the excited-to-Rydberg transition wavelength, the strength of the EIT feature on the lower-leg beam is strongly reduced in a Doppler-broadened medium. Here, we report on an alternative two-photon spectroscopic feature, which we term the two-photon Autler-Townes resonance, observed on the upper-leg beam. Compared to the EIT signal, this feature's superior signal-to-noise ratio allows one to resolve Rydberg resonances with principal quantum number as high as $n=80$. We also show that such a feature can be utilized to generate an error signal for stabilizing the frequency of the upper-leg beam.

quant-ph↗

arXiv2025

Impulse measurements enhanced with squeezed readout light

We quantify how squeezed light can reduce quantum measurement noise to levels below the standard quantum limit in impulse measurements with mechanical detectors. The broadband nature of the signal implies that frequency-dependent squeezing performs better than frequency-independent squeezing. We calculate the optimal scaling of the impulse sensitivity with the squeezing strength, and quantify degradations due to photodetection losses. Even for lossless measurement, we find there exists a fundamental limit to the benefit of squeezing that depends only on the system's mechanical properties.

quant-ph↗

arXiv2023

Circular orbits and polarized images of charged particles orbiting Kerr black hole with a weak magnetic field

In this work, we study circular motions of charged particles and their polarized images around the Kerr black hole immersed in a weak magnetic field. We pay special attention to the case that both the magnetic field and the charge-to-mass ratio are not big, thus the effective potential along the radial motion reduce to a cubic form approximately so that we can express the radius of the innermost stable circular orbit analytically in terms of the energy and angular momentum of charged particles. Moreover, we computed the polarized synchrotron radiations of these particles and obtained the polarized images semi-analytically for various spins, observational angles and prograde and retrograde orbits. In particular, We find that these parameters have significant impacts on the polarization rotation and the magnitude of the polarization flux.

gr-qc↗

arXiv2021

Correspondence of eikonal quasinormal modes and unstable fundamental photon orbits for Kerr-Newman black hole

In this work, we study the relation of the eikonal quasinormal modes (EQNMs) and the unstable fundamental photon orbits (UFPOs) in the Kerr-Newman spacetime. We find that in the eikonal limit the gravitational and electromagnetic perturbations of the Kerr-Newman black hole are naturally decoupled, and a single one-dimensional Schrödinger-like equation encoding the QNM spectrum can be derived. We then show that the decoupled Teukolsky master equation and the Klein-Gordon equation for the massless scalar field in the Kerr-Newman spacetime are of the same form in the eikonal limit. As a direct consequence, taking into account of the boundary conditions for EQNMs we show an exact correspondence between EQNMs and UFPOs, that is, EQNM/UFPO correspondence. More precisely, similar to the Kerr case, the real part of EQNM's frequency is a linear combination of the precessional and (polar) orbital frequencies, while the imaginary part of the frequency is proportional to the Lyapunov exponent of the UFPO.

gr-qc↗