Matthias Zens - Academia.edu (original) (raw)

Papers by Matthias Zens

Research paper thumbnail of Triggered Superradiance and Inversion Storage in a Hybrid Quantum System

arXiv (Cornell University), Jan 10, 2023

We study the superradiant emission of an inverted spin ensemble strongly coupled to a superconduc... more We study the superradiant emission of an inverted spin ensemble strongly coupled to a superconducting cavity. After fast inversion, we detune the spins from the cavity and store the inversion for tens of milliseconds, during which the remaining transverse spin components disappear. Switching back on resonance enables us to study the onset of superradiance. A weak trigger pulse of a few hundred photons shifts the superradiant burst to earlier times and imprints its phase onto the emitted radiation. For long hold times, the inversion decreases below the threshold for spontaneous superradiance. There, the energy stored in the ensemble can be used to amplify microwave pulses passing through the cavity.

Research paper thumbnail of Cumulant expansion approach to nonlinear dynamics of inhomogeneous ensembles in cavity QED

In the last couple of years much effort has been dedicated to the development and the investigati... more In the last couple of years much effort has been dedicated to the development and the investigation of hybrid quantum devices, which combine the advantages of very dissimilar quantum systems for the realization of efficient quantum computation and communication technologies. Particularly interesting in this regard are solid-state quantum memories based on ensembles of spins (e.g. nitrogen vacancy defects in diamond or rare-earth doped crystals) coupled to superconducting microwave cavities. Here the spin-ensemble acts as a robust memory where the collective coupling to the cavity mode allows for the coherent transfer of quantum information. The major downside of ensembles inside solid-state systems is their natural tendency to exhibit inhomogeneous broadening of the transition frequencies, which makes experiments as well as their theoretical description very challenging. On the theoretical side it is primarily the computational complexity due to the exponential growth of the associa...

Research paper thumbnail of Periodically Pulsed Quantum Light from a Superconducting Qubit Ensemble

Bulletin of the American Physical Society, 2019

Research paper thumbnail of Echo Trains in Pulsed Electron Spin Resonance of a Strongly Coupled Spin Ensemble

Physical Review Letters, 2020

Research paper thumbnail of Superabsorption by time-reversing superradiance

Nature Photonics, 2021

More atoms can not only absorb more light but, if prepared in a particular quantum state, can als... more More atoms can not only absorb more light but, if prepared in a particular quantum state, can also do so faster than single atoms. Now, researchers have experimentally demonstrated this time-reversed process of superradiance.

Research paper thumbnail of Periodic Cavity State Revivals from Atomic Frequency Combs

Physical Review Letters, 2021

Spin ensembles with a comb-shaped spectrum have shown exciting properties as efficient quantum me... more Spin ensembles with a comb-shaped spectrum have shown exciting properties as efficient quantum memories. Here, we present a rigorous theoretical study of such atomic frequency combs in the strong coupling limit of cavity QED, based on a full quantum treatment using tensor-network methods. Our results demonstrate that arbitrary multi-photon states in the cavity are almost perfectly absorbed by the spin ensemble and re-emitted as parity-flipped states at periodic time intervals. Fidelity values near unity are achieved in these revived states by compensating for energy shifts induced by the strong spin-cavity coupling through adjustments of individual coupling values of the teeth in the atomic frequency comb.

Research paper thumbnail of Variational Renormalization Group for Dissipative Spin-Cavity Systems: Periodic Pulses of Nonclassical Photons from Mesoscopic Spin Ensembles

Physical Review Letters, 2018

Mesoscopic spin ensembles coupled to a cavity offer the exciting prospect of observing complex no... more Mesoscopic spin ensembles coupled to a cavity offer the exciting prospect of observing complex nonclassical phenomena that pool the microscopic features from a few spins with those of macroscopic spin ensembles. Here, we demonstrate how the collective interactions in an ensemble of as many as hundred spins can be harnessed to obtain a periodic pulse train of nonclassical light. To unravel the full quantum dynamics and photon statistics, we develop a time-adaptive variational renormalization group method that accurately captures the underlying Lindbladian dynamics of the mesoscopic spin-cavity system.

Research paper thumbnail of Ultralong relaxation times in bistable hybrid quantum systems

Science Advances, 2017

Amplitude bistability in a solid-state hybrid quantum system shows critical slowing down with ult... more Amplitude bistability in a solid-state hybrid quantum system shows critical slowing down with ultralong relaxation times.

Research paper thumbnail of Sustained photon pulse revivals from inhomogeneously broadened spin ensembles

Laser & Photonics Reviews, 2016

A very promising recent trend in applied quantum physics is to combine the advantageous features ... more A very promising recent trend in applied quantum physics is to combine the advantageous features of different quantum systems into what is called "hybrid quantum technology". One of the key elements in this new field will have to be a quantum memory enabling to store quanta over extended periods of time. Systems that may fulfill the demands of such applications are comb-shaped spin ensembles coupled to a cavity. Due to the decoherence induced by the inhomogeneous ensemble broadening, the storage time of these quantum memories is, however, still rather limited. Here we demonstrate how to overcome this problem by burning well-placed holes into the spectral spin density leading to spectacular performance in the multimode regime. Specifically, we show how an initial excitation of the ensemble leads to the emission of more than a hundred well-separated photon pulses with a decay rate significantly below the fundamental limit of the recently proposed "cavity protection effect".

Research paper thumbnail of Critical phenomena and nonlinear dynamics in a spin ensemble strongly coupled to a cavity. I. Semiclassical approach

Physical Review A, 2019

We present a theoretical study on the nonlinear dynamics and stationary states of an inhomogeneou... more We present a theoretical study on the nonlinear dynamics and stationary states of an inhomogeneously broadened spin ensemble coupled to a single-mode cavity driven by an external drive with constant amplitude. Assuming a sizeable number of constituents within the ensemble allows us to use a semiclassical approach and to formally reduce the theoretical description to the Maxwell-Bloch equations for the cavity and spin amplitudes. We explore the critical slowing-down effect, quench dynamics, and asymptotic behavior of the system near a steady-state dissipative phase transition accompanied by a bistability effect. Some of our theoretical findings have recently been successfully verified in a specific experimental realization based on a spin ensemble of negatively charged nitrogen-vacancy centers in diamond strongly coupled to a single-mode microwave cavity (see Science Adv. 3, e1701626 (2017)).

Research paper thumbnail of Triggered Superradiance and Inversion Storage in a Hybrid Quantum System

arXiv (Cornell University), Jan 10, 2023

We study the superradiant emission of an inverted spin ensemble strongly coupled to a superconduc... more We study the superradiant emission of an inverted spin ensemble strongly coupled to a superconducting cavity. After fast inversion, we detune the spins from the cavity and store the inversion for tens of milliseconds, during which the remaining transverse spin components disappear. Switching back on resonance enables us to study the onset of superradiance. A weak trigger pulse of a few hundred photons shifts the superradiant burst to earlier times and imprints its phase onto the emitted radiation. For long hold times, the inversion decreases below the threshold for spontaneous superradiance. There, the energy stored in the ensemble can be used to amplify microwave pulses passing through the cavity.

Research paper thumbnail of Cumulant expansion approach to nonlinear dynamics of inhomogeneous ensembles in cavity QED

In the last couple of years much effort has been dedicated to the development and the investigati... more In the last couple of years much effort has been dedicated to the development and the investigation of hybrid quantum devices, which combine the advantages of very dissimilar quantum systems for the realization of efficient quantum computation and communication technologies. Particularly interesting in this regard are solid-state quantum memories based on ensembles of spins (e.g. nitrogen vacancy defects in diamond or rare-earth doped crystals) coupled to superconducting microwave cavities. Here the spin-ensemble acts as a robust memory where the collective coupling to the cavity mode allows for the coherent transfer of quantum information. The major downside of ensembles inside solid-state systems is their natural tendency to exhibit inhomogeneous broadening of the transition frequencies, which makes experiments as well as their theoretical description very challenging. On the theoretical side it is primarily the computational complexity due to the exponential growth of the associa...

Research paper thumbnail of Periodically Pulsed Quantum Light from a Superconducting Qubit Ensemble

Bulletin of the American Physical Society, 2019

Research paper thumbnail of Echo Trains in Pulsed Electron Spin Resonance of a Strongly Coupled Spin Ensemble

Physical Review Letters, 2020

Research paper thumbnail of Superabsorption by time-reversing superradiance

Nature Photonics, 2021

More atoms can not only absorb more light but, if prepared in a particular quantum state, can als... more More atoms can not only absorb more light but, if prepared in a particular quantum state, can also do so faster than single atoms. Now, researchers have experimentally demonstrated this time-reversed process of superradiance.

Research paper thumbnail of Periodic Cavity State Revivals from Atomic Frequency Combs

Physical Review Letters, 2021

Spin ensembles with a comb-shaped spectrum have shown exciting properties as efficient quantum me... more Spin ensembles with a comb-shaped spectrum have shown exciting properties as efficient quantum memories. Here, we present a rigorous theoretical study of such atomic frequency combs in the strong coupling limit of cavity QED, based on a full quantum treatment using tensor-network methods. Our results demonstrate that arbitrary multi-photon states in the cavity are almost perfectly absorbed by the spin ensemble and re-emitted as parity-flipped states at periodic time intervals. Fidelity values near unity are achieved in these revived states by compensating for energy shifts induced by the strong spin-cavity coupling through adjustments of individual coupling values of the teeth in the atomic frequency comb.

Research paper thumbnail of Variational Renormalization Group for Dissipative Spin-Cavity Systems: Periodic Pulses of Nonclassical Photons from Mesoscopic Spin Ensembles

Physical Review Letters, 2018

Mesoscopic spin ensembles coupled to a cavity offer the exciting prospect of observing complex no... more Mesoscopic spin ensembles coupled to a cavity offer the exciting prospect of observing complex nonclassical phenomena that pool the microscopic features from a few spins with those of macroscopic spin ensembles. Here, we demonstrate how the collective interactions in an ensemble of as many as hundred spins can be harnessed to obtain a periodic pulse train of nonclassical light. To unravel the full quantum dynamics and photon statistics, we develop a time-adaptive variational renormalization group method that accurately captures the underlying Lindbladian dynamics of the mesoscopic spin-cavity system.

Research paper thumbnail of Ultralong relaxation times in bistable hybrid quantum systems

Science Advances, 2017

Amplitude bistability in a solid-state hybrid quantum system shows critical slowing down with ult... more Amplitude bistability in a solid-state hybrid quantum system shows critical slowing down with ultralong relaxation times.

Research paper thumbnail of Sustained photon pulse revivals from inhomogeneously broadened spin ensembles

Laser & Photonics Reviews, 2016

A very promising recent trend in applied quantum physics is to combine the advantageous features ... more A very promising recent trend in applied quantum physics is to combine the advantageous features of different quantum systems into what is called "hybrid quantum technology". One of the key elements in this new field will have to be a quantum memory enabling to store quanta over extended periods of time. Systems that may fulfill the demands of such applications are comb-shaped spin ensembles coupled to a cavity. Due to the decoherence induced by the inhomogeneous ensemble broadening, the storage time of these quantum memories is, however, still rather limited. Here we demonstrate how to overcome this problem by burning well-placed holes into the spectral spin density leading to spectacular performance in the multimode regime. Specifically, we show how an initial excitation of the ensemble leads to the emission of more than a hundred well-separated photon pulses with a decay rate significantly below the fundamental limit of the recently proposed "cavity protection effect".

Research paper thumbnail of Critical phenomena and nonlinear dynamics in a spin ensemble strongly coupled to a cavity. I. Semiclassical approach

Physical Review A, 2019

We present a theoretical study on the nonlinear dynamics and stationary states of an inhomogeneou... more We present a theoretical study on the nonlinear dynamics and stationary states of an inhomogeneously broadened spin ensemble coupled to a single-mode cavity driven by an external drive with constant amplitude. Assuming a sizeable number of constituents within the ensemble allows us to use a semiclassical approach and to formally reduce the theoretical description to the Maxwell-Bloch equations for the cavity and spin amplitudes. We explore the critical slowing-down effect, quench dynamics, and asymptotic behavior of the system near a steady-state dissipative phase transition accompanied by a bistability effect. Some of our theoretical findings have recently been successfully verified in a specific experimental realization based on a spin ensemble of negatively charged nitrogen-vacancy centers in diamond strongly coupled to a single-mode microwave cavity (see Science Adv. 3, e1701626 (2017)).