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Predicting quantum dynamical cost landscapes with deep learning
Mogens Dalgaard, Felix Motzoi, Jacob Sherson
State-of-the-art quantum algorithms routinely tune dynamically parametrized cost functionals for combinatorics, machine learning, equation-solving, or energy minimization. However,…
Achieving fast high-fidelity optimal control of many-body quantum dynamics
Jesper Hasseriis Mohr Jensen, Frederik Skovbo Møller, Jens Jakob Sørensen +1
We demonstrate the efficiency of a recent exact-gradient optimal control methodology by applying it to a challenging many-body problem, crossing the superfluid to Mott-insulator ph…
Hessian-based optimization of constrained quantum control
Mogens Dalgaard, Felix Motzoi, Jesper Hasseriis Mohr Jensen +1
Efficient optimization of quantum systems is a necessity for reaching fault tolerant thresholds. A standard tool for optimizing simulated quantum dynamics is the gradient-based \te…
Approximate Dynamics Lead to More Optimal Control: Efficient Exact Derivatives
Jesper Hasseriis Mohr Jensen, Frederik Skovbo Møller, Jens Jakob Sørensen +1
Accurate derivatives are important for efficiently locally traversing and converging in quantum optimization landscapes. By deriving analytically exact control derivatives (gradien…
Crowdsourcing human common sense for quantum control
Jesper Hasseriis Mohr Jensen, Miroslav Gajdacz, Shaeema Zaman Ahmed +6
Citizen science methodologies have over the past decade been applied with great success to help solve highly complex numerical challenges. Here, we take early steps in the quantum…
Optimization of Pulses with Low Bandwidth for Improved Excitation of Multiple-Quantum Coherences in NMR of Quadrupolar Nuclei
Jens Jakob Sørensen, Jacob Søgaard Nyemann, Felix Motzoi +2
We discuss the commonly encountered problem when optimizing NMR pulses using optimal control that the otherwise very precise NMR theory does not provide as excellent agreement with…
(Of course) algorithms beat gamers at solving quantum control problems
Klaus Mølmer, Jacob Sherson
Dries Sels and Allan Grønlund have demonstrated numerical algorithms that outperform the players of our Quantum Moves game and they call the conclusions of our article Exploring th…
Time-Optimal Control of Collisional Gates in Ultracold Atomic Systems
Jesper Hasseriis Mohr Jensen, Jens Jakob Sørensen, Klaus Mølmer +1
We use quantum optimal control to identify fast collision-based two-qubit gates in ultracold atoms. We show that a significant speed up can be achieved by opti…
Global optimization of quantum dynamics with AlphaZero deep exploration
Mogens Dalgaard, Felix Motzoi, Jens Jakob Sorensen +1
While a large number of algorithms for optimizing quantum dynamics for different objectives have been developed, a common limitation is the reliance on good initial guesses, being…
Single-shot determination of quantum phases via continuous measurements
Aniket Patra, Lukas F. Buchmann, Felix Motzoi +3
We propose that weak continuous probing may be exploited to determine and define quantum phases of complex many-body systems based on the measurement record alone. We test the resu…
QEngine: An open-source C++ Library for Quantum Optimal Control of Ultracold Atoms
Jens Jakob Sørensen, Jesper Jensen, Till Heinzel +1
We present the first version of the QEngine, an open-source C++ library for simulating and controlling ultracold quantum systems using optimal control theory (OCT). The most notabl…
Quantum Control with Measurements and Quantum Zeno Dynamics
Jens Jakob Sørensen, Mogens Dalgaard, Alexander Holm Kiilerich +2
We introduce an efficient iterative method to prepare a target state in Hilbert spaces with high dimensionality using a combination of unitary evolution, measurements, and quantum…
Approaching the Quantum Speed Limit with Global-Local Optimization
Jens Jakob Sørensen, Mikel Aranburu, Till Heinzel +1
We propose a Global-Local optimization algorithm for quantum control that combines standard local search methodologies with evolutionary algorithms. This allows us to find faster s…
Quantum Optimal Control in a Chopped Basis: Applications in Control of Bose-Einstein Condensates
Jens Jakob Sørensen, Mikel Aranburu, Till Heinzel +1
We discuss quantum optimal control of Bose-Einstein condensates trapped in magnetic microtraps. The objective is to transfer a condensate from the ground state to the first-excited…
Fast state transfer in a Λ-system: a shortcut-to-adiabaticity approach to robust and resource optimized control
Henrik Lund Mortensen, Jens Jakob W. H. Sørensen, Klaus Mølmer +1
We propose an efficient strategy to find optimal control functions for state-to-state quantum control problems. Our procedure first chooses an input state trajectory, that can real…
Measurement-enhanced determination of BEC phase transitions
Mark G. Bason, Robert Heck, Mario Napolitano +6
We demonstrate how dispersive atom number measurements during evaporative cooling can be used for enhanced determination of the parameter dependence of the transition to a Bose-Ein…
Manipulating matter waves in an optical superlattice
Brendan Reid, Maria Moreno-Cardoner, Jacob Sherson +1
We investigate the potential for controlling a non-interacting Bose-Einstein condensate loaded into a one-dimensional optical superlattice. Our control strategy combines Bloch osci…
Manipulation of collective quantum states in Bose-Einstein condensates by continuous imaging
Andrew C. J. Wade, Jacob F. Sherson, Klaus Mølmer
We develop a Gaussian state treatment that allows a transparent quantum description of the continuous, nondestructive imaging of and feedback on a Bose-Einstein condensate. We have…
Squeezing and entanglement of density oscillations in a Bose-Einstein condensate
Andrew C. J. Wade, Jacob F. Sherson, Klaus Mølmer
The dispersive interaction of atoms and a far-detuned light field allows nondestructive imaging of the density oscillations in Bose-Einstein condensates. Starting from a ground sta…
Many-body state engineering using measurements and fixed unitary dynamics
Mads Kock Pedersen, Jens Jakob W. H. Sørensen, Malte C. Tichy +1
We develop a scheme to prepare a desired state or subspace in high-dimensional Hilbert-spaces using repeated applications of a single static projection operator onto the desired ta…
Time limited optimal dynamics beyond the Quantum Speed Limit
Miroslav Gajdacz, Kunal K. Das, Jan Arlt +2
The quantum speed limit sets the minimum time required to transfer a quantum system completely into a given target state. At shorter times the higher operation speed has to be paid…
Single- and two-qubit quantum gates using superimposed optical lattice potentials
Nils B. Jørgensen, Mark G. Bason, Jacob F. Sherson
Steps towards implementing a collision based two-qubit gate in optical lattices have previously been realized by the parallel merging all pairs of atoms in a periodicity two superl…
Non-adiabatic many-atom quantum state control in few-well systems
Malte C. Tichy, Mads Kock Pedersen, Klaus Mølmer +1
We present a fast scheme for arbitrary unitary control of interacting bosonic atoms in a double-well. Assuming fixed inter-well tunnelling rate and intra-well interaction strength,…
Dynamical control of matter wave splitting using time-dependent optical lattices
Sung Jong Park, Henrik Kjaer Andersen, Sune Mai +2
We report on measurements of splitting Bose-Einstein condensates (BEC) by using a time-dependent optical lattice potential. First, we demonstrate the division of a BEC into a set o…