511 citations · 4k across the 79 of their papers we have counts for
31 papers · 1 filter
Macroscopic quantum synchronization effects
Tobias Nadolny, Christoph Bruder
We theoretically describe macroscopic quantum synchronization effects occurring in a network of all-to-all coupled quantum limit-cycle oscillators. The coupling causes a transition…
Improving Transmon Qudit Measurement on IBM Quantum Hardware
Tobias Kehrer, Tobias Nadolny, Christoph Bruder
The Hilbert space of a physical qubit typically features more than two energy levels. Using states outside the qubit subspace can provide advantages in quantum computation. To bene…
Mapping out phase diagrams with generative classifiers
Julian Arnold, Frank Schäfer, Alan Edelman +1
One of the central tasks in many-body physics is the determination of phase diagrams. However, mapping out a phase diagram generally requires a great deal of human intuition and un…
Geometric Phase in Quantum Synchronization
Aaron Daniel, Christoph Bruder, Martin Koppenhöfer
We consider a quantum limit-cycle oscillator implemented in a spin system whose quantization axis is slowly rotated. Using a kinematic approach to define geometric phases in nonuni…
Optical coherent feedback control of a mechanical oscillator
Maryse Ernzer, Manel Bosch Aguilera, Matteo Brunelli +5
Feedback is a powerful and ubiquitous technique both in classical and quantum system control. Its standard implementation relies on measuring the state of a system, processing the…
Half-integer vs. integer effects in quantum synchronization of spin systems
Ryan Tan, Christoph Bruder, Martin Koppenhöfer
We study the quantum synchronization of a single spin driven by an external semiclassical signal for spin numbers larger than , the smallest system to host a quantum self-su…
Control of Stochastic Quantum Dynamics by Differentiable Programming
Frank Schäfer, Pavel Sekatski, Martin Koppenhöfer +2
Control of the stochastic dynamics of a quantum system is indispensable in fields such as quantum information processing and metrology. However, there is no general ready-made appr…
A differentiable programming method for quantum control
Frank Schäfer, Michal Kloc, Christoph Bruder +1
Optimal control is highly desirable in many current quantum systems, especially to realize tasks in quantum information processing. We introduce a method based on differentiable pr…
Quantum Synchronization on the IBM Q System
Martin Koppenhöfer, Christoph Bruder, Alexandre Roulet
We report the first experimental demonstration of quantum synchronization. This is achieved by performing a digital simulation of a single spin- limit-cycle oscillator on the qu…
Heralded dissipative preparation of nonclassical states in a Kerr oscillator
Martin Koppenhöfer, Christoph Bruder, Niels Lörch
We present a heralded state preparation scheme for driven nonlinear open quantum systems. The protocol is based on a continuous photon counting measurement of the system's decay ch…
Quantum state preparation for coupled period tripling oscillators
Niels Lörch, Yaxing Zhang, Christoph Bruder +1
We investigate the quantum transition to a correlated state of coupled oscillators in the regime where they display period tripling in response to a drive at triple the eigenfreque…
Unraveling nonclassicality in the optomechanical instability
Martin Koppenhöfer, Christoph Bruder, Niels Lörch
Conditional dynamics due to continuous optical measurements has successfully been applied for state reconstruction and feedback cooling in optomechanical systems. In this article,…
Quantum synchronization and entanglement generation
Alexandre Roulet, Christoph Bruder
We study synchronization in a two-node network built out of the smallest possible self-sustained oscillator: a spin 1. We first demonstrate that phase locking between the quantum o…
Optimal work extraction from quantum states by photo-assisted Cooper pair tunneling
Niels Lörch, Christoph Bruder, Nicolas Brunner +1
The theory of quantum thermodynamics predicts fundamental bounds on work extraction from quantum states. As these bounds are derived in a very general and abstract setting, it is u…
Synchronizing the Smallest Possible System
Alexandre Roulet, Christoph Bruder
We investigate the minimal Hilbert-space dimension for a system to be synchronized. We first show that qubits cannot be synchronized due to the lack of a limit cycle. Moving to lar…
Quantum effects in amplitude death of coupled anharmonic self-oscillators
Ehud Amitai, Martin Koppenhöfer, Niels Lörch +1
Coupling two or more self-oscillating systems may stabilize their zero-amplitude rest-state, therefore quenching their oscillation. This phenomenon is termed "amplitude death". Wel…
Quantum Synchronization Blockade: Energy Quantization hinders Synchronization of Identical Oscillators
Niels Lörch, Simon E. Nigg, Andreas Nunnenkamp +2
Classically, the tendency towards spontaneous synchronization is strongest if the natural frequencies of the self-oscillators are as close as possible. We show that this wisdom fai…
Synchronization of an optomechanical system to an external drive
Ehud Amitai, Niels Lörch, Andreas Nunnenkamp +2
Optomechanical systems driven by an effective blue detuned laser can exhibit self-sustained oscillations of the mechanical oscillator. These self-oscillations are a prerequisite fo…
Optomechanical Self-Oscillations in an Anharmonic Potential: Engineering a Nonclassical Steady State
Manuel Grimm, Christoph Bruder, Niels Lörch
We study self-oscillations of an optomechanical system, where coherent mechanical oscillations are induced by a driven optical or microwave cavity, for the case of an anharmonic me…
Genuine quantum signatures in synchronization of anharmonic self-oscillators
Niels Lörch, Ehud Amitai, Andreas Nunnenkamp +1
We study the synchronization of a van der Pol self-oscillator with Kerr anharmonicity to an external drive. We demonstrate that the anharmonic, discrete energy spectrum of the quan…
Detection of weak forces based on noise-activated switching in bistable optomechanical systems
Samuel Aldana, Christoph Bruder, Andreas Nunnenkamp
We propose to use cavity optomechanical systems in the regime of optical bistability for the detection of weak harmonic forces. Due to the optomechanical coupling an external force…
Equivalence between an optomechanical system and a Kerr medium
Samuel Aldana, Christoph Bruder, Andreas Nunnenkamp
We study the optical bistability of an optomechanical system in which the position of a mechanical oscillator modulates the cavity frequency. The steady-state mean-field equation o…
Strategy for implementing stabilizer-based codes on solid-state qubits
Tetsufumi Tanamoto, Vladimir M. Stojanović, Christoph Bruder +1
We present a method for implementing stabilizer-based codes with encoding schemes of the operator quantum error correction paradigm, e.g., the "standard" five-qubit and CSS codes,…
Strong-coupling effects in dissipatively coupled optomechanical systems
Talitha Weiss, Christoph Bruder, Andreas Nunnenkamp
In this paper we study cavity optomechanical systems in which the position of a mechanical oscillator modulates both the resonance frequency (dispersive coupling) and the linewidth…