arXiv subjects

K. -M. Hsieh

Publications and source records attributed to K. -M. Hsieh.

4 recordsLinked to original sources

arXiv2025

Realizing on-demand all-to-all selective interactions between distant spin ensembles

Achieving all-to-all coherent networks is critical for the advancement of large-scale coherent computing and communication protocols. By exploiting the resonant dipole-dipole interaction between distant spin ensembles coupled to a one-dimensional coplanar waveguide (CPW) terminated by a mirror, we successfully demonstrate an on-demand all-to-all selective coherent network between four spin ensembles. Furthermore, by repositioning the spin ensembles along the CPW, we achieve collective coupling, and demonstrate coherent energy exchange between multiple spin ensembles in the time domain. These results strongly indicate the potential of this device as a medium-scale all-to-all network structure, which is poised to advance the exploration of many-body physics and enhance coherent information processing capabilities.

physics.app-ph↗

arXiv2025

Tunable coherent microwave beam splitter and combiner at the single-photon level

A beam splitter is a key component used to direct and combine light paths in various optical and microwave systems. It plays a crucial role in devices like interferometers, such as the Mach-Zehnder and Hong-Ou-Mandel setups, where it splits light into different paths for interference measurements. These measurements are vital for precise phase and coherence testing in both classical and quantum optical experiments. In this work, we present a nonlinear beam splitter and beam combiner utilizing a frequency-tunable superconducting artificial atom in a one-dimensional open waveguide. This beam splitter is highly versatile, with adjustable transparency ranging from unity to zero for signals at the single-photon level. Additionally, the beam combiner can merge two coherent beams, generating interference fringes as the relative phase between them varies.

quant-ph↗

arXiv2024

Group delay controlled by the decoherence of a single artificial atom

The ability to slow down light at the single-photon level has applications in quantum information processing and other quantum technologies. We demonstrate two methods, both using just a single artificial atom, enabling dynamic control over microwave light velocities in waveguide quantum electrodynamics (waveguide QED). Our methods are based on two distinct mechanisms harnessing the balance between radiative and non-radiative decay rates of a superconducting artificial atom in front of a mirror. In the first method, we tune the radiative decay of the atom using interference effects due to the mirror; in the second method, we pump the atom to control its non-radiative decay through the Autler--Townes effect. When the half the radiative decay rate exceeds the non-radiative decay rate, we observe positive group delay; conversely, dominance of the non-radiative decay rate results in negative group delay. Our results advance signal-processing capabilities in waveguide QED.

quant-ph↗

arXiv2024

Tuning atom-field interaction via phase shaping

A coherent electromagnetic field can be described by its amplitude, frequency, and phase. All these properties can influence the interaction between the field and an atom. Here we demonstrate the phase shaping of microwaves that are scattered by a superconducting artificial atom coupled to the end of a semi-infinite 1D transmission line. In particular, we input a weak exponentially rising pulse with phase modulation to a transmon qubit. We observe that field-atom interaction can be tuned from nearly full interaction (interaction efficiency, i.e., amount of the field energy interacting with the atom, of 94.5%) to effectively no interaction (interaction efficiency 3.5%).

quant-ph↗