213 citations · 1.3k across the 40 of their papers we have counts for
27 papers · 1 filter
Reconstructing the unitary part of a noisy quantum channel
Adrian Romer, Daniel M. Reich, Christiane P. Koch
We consider the problem of reconstructing the unitary describing the evolution of a quantum system, or quantum channel, from a set of input and output states. For ideal, fully cohe…
Determining the ability for universal quantum computing: Testing controllability via dimensional expressivity
Fernando Gago-Encinas, Tobias Hartung, Daniel M. Reich +2
Operator controllability refers to the ability to implement an arbitrary unitary in SU(N) and is a prerequisite for universal quantum computing. Controllability tests can be used i…
Optimizing for an arbitrary Schrödinger cat state. II. Application in the presence of dissipation
Matthias G. Krauss, Daniel M. Reich, Christiane P. Koch
We extend here the optimization functional targeting arbitrary cat states, derived in the companion paper, to open quantum system dynamics. Applying it to a Jaynes-Cummings model w…
Optimizing for an arbitrary Schrödinger cat state
Matthias G. Krauss, Christiane P. Koch, Daniel M. Reich
We derive a set of functionals for optimization towards an arbitrary cat state and demonstrate their application by optimizing the dynamics of a Kerr-nonlinear Hamiltonian with two…
Fundamental Bounds on Qubit Reset
Daniel Basilewitsch, Jonas Fischer, Daniel M. Reich +2
Qubit reset is a basic prerequisite for operating quantum devices, requiring the export of entropy. The fastest and most accurate way to reset a qubit is obtained by coupling the q…
Krotov: A Python implementation of Krotov's method for quantum optimal control
Michael H. Goerz, Daniel Basilewitsch, Fernando Gago-Encinas +4
We present a new open-source Python package, krotov, implementing the quantum optimal control method of that name. It allows to determine time-dependent external fields for a wide…
Optimized Sampling of Mixed-State Observables
Marec W. Heger, Christiane P. Koch, Daniel M. Reich
Quantum dynamical simulations of statistical ensembles pose a significant computational challenge due to the fact that mixed states need to be represented. If the underlying dynami…
Quantum Optimal Control for Mixed State Squeezing in Cavity Optomechanics
Daniel Basilewitsch, Christiane P. Koch, Daniel M. Reich
The performance of key tasks in quantum technology, such as accurate state preparation, can be maximized by utilizing external controls and deriving their shape with optimal contro…
Fast and accurate circularization of a Rydberg atom
Sabrina Patsch, Daniel M. Reich, Jean-Michel Raimond +3
Preparation of a so-called circular state in a Rydberg atom where the projection of the electron angular momentum takes its maximum value is challenging due to the required amount…
Hybrid benchmarking of arbitrary quantum gates
Tobias Chasseur, Daniel M. Reich, Christiane P. Koch +1
We present a protocol for Interleaved Randomized Benchmarking of arbitrary quantum gates using Monte Carlo sampling of quantum states. It is generally applicable, including non-Cli…
Optimizing for an arbitrary perfect entangler. II. Application
Michael H. Goerz, Giulia Gualdi, Daniel M. Reich +7
The difficulty of an optimization task in quantum information science depends on the proper mathematical expression of the physical target. Here we demonstrate the power of optimiz…
Optimizing for an arbitrary perfect entangler: I. Functionals
Paul Watts, Jiří Vala, Matthias M. Müller +5
Optimal control theory is a powerful tool for improving figures of merit in quantum information tasks. Finding the solution to any optimal control problem via numerical optimizatio…
Exploiting Non-Markovianity of the Environment for Quantum Control
Daniel M. Reich, Nadav Katz, Christiane P. Koch
When the environment of an open quantum system is non-Markovian, amplitude and phase flow not only from the system into the environment but also back. Here we show that this featur…
Optimal quantum control of Bose-Einstein condensates in magnetic microtraps: Comparison of GRAPE and Krotov optimization schemes
Georg Jäger, Daniel Reich, Michael H. Goerz +2
We study optimal quantum control of the dynamics of trapped Bose-Einstein condensates: The targets are to split a condensate, residing initially in a single well, into a double wel…
Arbitrary quantum-state preparation of a harmonic oscillator via optimal control
Katharina Rojan, Daniel M. Reich, Igor Dotsenko +3
The efficient initialization of a quantum system is a prerequisite for quantum technological applications. Here we show that several classes of quantum states of a harmonic oscilla…
Optimal qudit operator bases for efficient characterization of quantum gates
Daniel M. Reich, Giulia Gualdi, Christiane P. Koch
For certain quantum operations acting on qubits, there exist bases of measurement operators such that estimating the average fidelity becomes efficient. The number of experiments r…
Efficient Monte Carlo characterization of quantum operations for qudits
Giulia Gualdi, David Licht, Daniel M. Reich +1
For qubits, Monte Carlo estimation of the average fidelity of Clifford unitaries is efficient -- it requires a number of experiments that is independent of the number of qubits…
Optimal control theory for a unitary operation under dissipative evolution
Michael H. Goerz, Daniel M. Reich, Christiane P. Koch
We show that optimizing a quantum gate for an open quantum system requires the time evolution of only three states irrespective of the dimension of Hilbert space. This represents a…
Steering the optimization pathway in the control landscape using constraints
José P. Palao, Daniel M. Reich, Christiane P. Koch
We show how additional constraints, restricting the spectrum of the optimized pulse or confining the system dynamics, can be used to steer optimization in quantum control towards d…
Optimal quantum control of Bose-Einstein condensates in magnetic microtraps: Consideration of filter effects
Georg Jäger, Ulrich Hohenester
We theoretically investigate protocols based on optimal control theory (OCT) for manipulating Bose-Einstein condensates in magnetic microtraps, using the framework of the Gross-Pit…
Cooling molecular vibrations with shaped laser pulses: Optimal control theory exploiting the timescale separation between coherent excitation and spontaneous emission
Daniel M. Reich, Christiane P. Koch
Laser cooling of molecules employing broadband optical pumping involves a timescale separation between laser excitation and spontaneous emission. Here, we optimize the optical pump…
Optimal control under spectral constraints: Enforcing multi-photon absorption pathways
Daniel M. Reich, José P. Palao, Christiane P. Koch
Shaped pulses obtained by optimal control theory often possess unphysically broad spectra. In principle, the spectral width of a pulse can be restricted by an additional constraint…
Optimal strategies for estimating the average fidelity of quantum gates
Daniel M. Reich, Giulia Gualdi, Christiane P. Koch
We show that the minimum experimental effort to characterize the proper functioning of a quantum device scales as 2^n for n qubits and requires classical computational resources ~…
Minimum number of input states required for quantum gate characterization
Daniel M. Reich, Giulia Gualdi, Christiane P. Koch
We derive an algebraic framework which identifies the minimal information required to assess how well a quantum device implements a desired quantum operation. Our approach is based…