Resources
Software for designing and simulating controls, what to read first, the field's vocabulary, and how it came to be.
Software
Open-source packages unless marked otherwise. Every link was checked; where a package has a paper, it is cited.
Optimal-control frameworks
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qutip-qoc Python
GRAPE, CRAB, GOAT and JAX-based optimization of controls, built on QuTiP.
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krotov Python
Reference implementation of Krotov’s method for closed and open systems, built on QuTiP.
Krotov: A Python implementation of Krotov's method for quantum optimal control SciPost Phys. 7, 080 (2019) doi
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QuantumControl.jl Julia
Framework for quantum dynamics and control, with GRAPE.jl, Krotov.jl and QuantumPropagators.jl; supports semi-automatic differentiation of arbitrary figures of merit.
Quantum Optimal Control via Semi-Automatic Differentiation Quantum 6, 871 (2022) doi
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QuOCS Python
Quantum optimal control suite (dCRAB, GRAPE, automatic differentiation) designed to talk to experiments.
QuOCS: The quantum optimal control suite Computer Physics Communications 291, 108782 (2023) doi
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C3 Python
Toolset that combines open-loop optimization, closed-loop calibration and model learning (TensorFlow).
Integrated Tool Set for Control, Calibration, and Characterization of Quantum Devices Applied to Superconducting Qubits Phys. Rev. Applied 15, 034080 (2021) doi
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qopt Python
Qubit simulation and optimal control with realistic noise models, oriented towards experiments.
qopt: An Experiment-Oriented Software Package for Qubit Simulation and Quantum Optimal Control Phys. Rev. Applied 17, 034036 (2022) doi
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Piccolo.jl Julia
Quantum optimal control by direct collocation, solved with an interior-point method.
Direct Collocation for Quantum Optimal Control preprint (2023) arXiv:2305.03261
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Juqbox.jl Julia
Optimal control of closed systems with B-spline envelopes and carrier waves.
Optimal Control of Closed Quantum Systems via B-Splines with Carrier Waves SIAM J. Sci. Comput. 44, A3592-A3616 (2022) doi
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Quandary C++
High-performance optimal control of open quantum systems (Lindblad), parallelized with MPI.
Quandary: An open-source C++ package for high-performance optimal control of open quantum systems 2021 IEEE/ACM Second International Workshop on Quantum Computing Software (QCS), 88-98 (2021) doi
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Spinach MATLAB
Spin-dynamics simulation for magnetic resonance, with GRAPE optimal control built in.
Spinach – A software library for simulation of spin dynamics in large spin systems Journal of Magnetic Resonance 208, 179-194 (2011) doi
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QControlPolyOpt Julia
Global optimization of quantum control problems as polynomial optimization (QCPOP).
Globally optimal control of quantum dynamics Phys. Rev. Research 7, 043202 (2025) doi · arXiv:2209.05790
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ECD_control Python
Optimization of echoed conditional-displacement sequences for an oscillator coupled to a qubit.
Fast universal control of an oscillator with weak dispersive coupling to a qubit Nat. Phys. 18, 1464-1469 (2022) doi
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Boulder Opal Python · commercial
Commercial software from Q-CTRL for autonomous calibration and control of quantum hardware (cloud service with a Python client).
Simulation and differentiable dynamics
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QuTiP Python
The Quantum Toolbox in Python — closed and open dynamics, the basis of many control packages.
QuTiP: An open-source Python framework for the dynamics of open quantum systems Computer Physics Communications 183, 1760-1772 (2012) doi · arXiv:1110.0573 QuTiP 5: The Quantum Toolbox in Python Physics Reports 1153, 1-62 (2026) doi · arXiv:2412.04705
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QuantumToolbox.jl Julia
QuTiP-style toolbox for quantum dynamics in Julia.
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dynamiqs Python
GPU-accelerated, differentiable solvers for closed and open systems, built on JAX.
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quantum-optimal-control Python
GRAPE with automatic differentiation on GPUs (TensorFlow); the code of the paper below, not actively maintained.
Speedup for quantum optimal control from automatic differentiation based on graphics processing units Phys. Rev. A 95, 042318 (2017) doi
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DYNAMO MATLAB
Unified framework for comparing and benchmarking gradient algorithms (GRAPE, Krotov and hybrids); last updated 2011.
Comparing, optimizing, and benchmarking quantum-control algorithms in a unifying programming framework Phys. Rev. A 84, 022305 (2011) doi
Pulse sequences and noise
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Q-CTRL Open Controls Python
Open library of dynamical-decoupling sequences and composite pulses.
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filter_functions Python
Generalized filter functions and quantum processes of gate sequences under classical noise.
Filter-function formalism and software package to compute quantum processes of gate sequences for classical non-Markovian noise Phys. Rev. Research 3, 043047 (2021) doi
Platforms and hardware
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Pulser Python
Pulse-level and analog programming of neutral-atom arrays, with emulation.
Pulser: An open-source package for the design of pulse sequences in programmable neutral-atom arrays Quantum 6, 629 (2022) doi
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qutip-qip Python
Compiles circuits to pulses on simulated processors and simulates them with noise.
Pulse-level noisy quantum circuits with QuTiP Quantum 6, 630 (2022) doi
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PennyLane Python
Differentiable quantum programming, including pulse programs with parametrized Hamiltonians.
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QICK Python
Firmware and software for RFSoC-based qubit control and readout.
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Qibolab Python
Drivers and pulse execution for several control-electronics platforms.
General numerical tools
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JAX Python
Automatic differentiation and GPU/TPU compilation; the engine of several packages above.
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SciPy optimize Python
L-BFGS-B, trust-region and other optimizers used by many Python control codes.
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NLopt C
Library of local and global, gradient-based and derivative-free optimizers.
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pycma Python
Reference implementation of the CMA-ES evolution strategy.
Completely Derandomized Self-Adaptation in Evolution Strategies Evolutionary Computation 9, 159-195 (2001) doi
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TSSOS Julia
Sparse moment–SOS hierarchy for global polynomial optimization.
Reading
Start here
Reviews and tutorials that introduce the whole field.
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The 2015 European roadmap — state of the art, goals and open challenges, across platforms.
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Quantum optimal control in quantum technologies. Strategic report on current status, visions and goals for research in Europe EPJ Quantum Technol. 9, 19 (2022) doi
The 2022 update of the roadmap, with a long list of open questions in controllability and control design.
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Introduction to theoretical and experimental aspects of quantum optimal control J. Phys. B: At. Mol. Opt. Phys. 57, 133001 (2024) doi · arXiv:2403.00532
A recent introduction to the theory and the experimental practice of optimal control.
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Past, present and future of controlling quantum phenomena, from chemistry to quantum information.
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A compact tutorial on quantum optimal control theory and its numerical methods.
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Quantum control theory and applications: a survey IET Control Theory Appl. 4, 2651-2671 (2010) doi · arXiv:0910.2350
A survey from the control-engineering side — controllability, feedback, robust and learning control.
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A tutorial on optimal control and reinforcement learning methods for quantum technologies Physics Letters A 434, 128054 (2022) doi
Tutorial on optimal control and reinforcement learning methods for quantum technologies.
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Introduction to the Pontryagin Maximum Principle for Quantum Optimal Control PRX Quantum 2, 030203 (2021) doi
Pontryagin’s maximum principle explained for quantum control, with worked examples.
Books
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Mathematical introduction to quantum control — Lie-algebraic controllability, optimal control, dynamics.
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The standard text on quantum measurement and feedback control.
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Coherent control of molecular processes, from the founders of the interference approach.
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Geometric control theory — reachable sets, the maximum principle, sub-Riemannian problems.
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Linear quantum systems and coherent feedback.
Reviews by topic
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Controlling open quantum systems: tools, achievements, and limitations J. Phys.: Condens. Matter 28, 213001 (2016) doi
Control of open quantum systems — tools, achievements and limitations.
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Quantum control landscapes — critical points and what they mean for optimization.
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One decade of quantum optimal control in the chopped random basis Rep. Prog. Phys. 85, 076001 (2022) doi
Ten years of the chopped random basis (CRAB) method.
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Shortcuts to adiabaticity: Concepts, methods, and applications Rev. Mod. Phys. 91, 045001 (2019) doi
Shortcuts to adiabaticity — concepts, methods and applications.
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Stimulated Raman adiabatic passage in physics, chemistry, and beyond Rev. Mod. Phys. 89, 015006 (2017) doi
Stimulated Raman adiabatic passage and its many uses.
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Quantum speed limits: from Heisenberg’s uncertainty principle to optimal quantum control J. Phys. A: Math. Theor. 50, 453001 (2017) doi
Quantum speed limits, from the uncertainty principle to optimal control.
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Review of Decoherence‐Free Subspaces, Noiseless Subsystems, and Dynamical Decoupling Quantum Information and Computation for Chemistry, 295-354 (2014) doi
Decoherence-free subspaces, noiseless subsystems and dynamical decoupling.
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NMR techniques for quantum control and computation — where many control ideas were first tested.
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Quantum control of molecular rotation.
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From Pulses to Circuits and Back Again: A Quantum Optimal Control Perspective on Variational Quantum Algorithms PRX Quantum 2, 010101 (2021) doi
Variational quantum algorithms seen as optimal control problems.
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Introduction to quantum optimal control for quantum sensing with nitrogen-vacancy centers in diamond AVS Quantum Science 2, 024701 (2020) doi
Optimal control for quantum sensing with NV centres.
Landmark papers
A small selection; the timeline below gives more.
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Optimal control of quantum-mechanical systems: Existence, numerical approximation, and applications Phys. Rev. A 37, 4950-4964 (1988) doi
Optimal control theory formulated for quantum-mechanical systems.
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Closed-loop learning control — let the experiment optimize the pulse.
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Time-optimal control of coupled spins by geometric methods.
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Optimal control of coupled spin dynamics: design of NMR pulse sequences by gradient ascent algorithms Journal of Magnetic Resonance 172, 296-305 (2005) doi
GRAPE, the gradient algorithm used everywhere.
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Why optimal control is easy so often — trap-free landscapes.
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Optimal control at the quantum speed limit.
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CRAB — optimal control for many-body dynamics with few parameters.
Every topic article ends with the key papers on that topic.
Glossary
- Average gate fidelity
- The fidelity between an implemented operation and a target gate, averaged uniformly over all pure input states. For a \(d\)-dimensional system it is an affine function of the entanglement fidelity, which makes it simple to compute (Nielsen’s formula). → Problem formulation & figures of merit, Quantum gate synthesis
- Bilinear control system
- Dynamics of the form \(\dot x = (A + \sum_k u_k(t) B_k)\,x\) — linear in the state and in the controls separately. The Schrödinger equation \(i\dot\psi = (H_0 + \sum_k u_k(t) H_k)\psi\) is the standard example. → Quantum controllability
- Closed-loop (learning) control
- Optimization in which every candidate control is tried on the experiment and the measured figure of merit is fed back to the optimizer; no accurate model is needed. → Closed-loop & in-situ optimization
- Coherent feedback
- Feedback in which the controller is itself a quantum system, connected to the plant without measurement — for example through optical fields. → Linear quantum systems & coherent feedback, Measurement-based feedback
- Composite pulse
- A sequence of simple rotations whose errors cancel to some order, so that the whole sequence is robust to a systematic error (amplitude, detuning) that would spoil a single pulse. → Composite pulses
- Control landscape
- The figure of merit viewed as a function of the controls. Its critical points — and whether it has traps — decide how hard an optimization is. → Control landscapes
- Controllability
- The property that every target (state, or unitary) can be reached with admissible controls. For finite-dimensional closed systems it is decided by the Lie algebra generated by the drift and control Hamiltonians. → Quantum controllability
- Counterdiabatic driving
- An added Hamiltonian that cancels the non-adiabatic transitions of a time-dependent Hamiltonian, so that the system follows its instantaneous eigenstates at any speed. Also called transitionless driving. → Shortcuts to adiabaticity
- CRAB
- Chopped RAndom Basis: the control is expanded in a few randomized basis functions, and the coefficients are optimized, often without gradients. dCRAB changes the basis during the optimization. → CRAB & dCRAB
- DRAG
- Derivative Removal by Adiabatic Gate: adding a quadrature component proportional to the derivative of the pulse envelope suppresses leakage and phase errors in weakly anharmonic qubits such as transmons. → DRAG & leakage suppression
- Drift Hamiltonian
- The part of the Hamiltonian that cannot be switched off, \(H_0\) in \(H(t) = H_0 + \sum_k u_k(t)H_k\). A drift outside the control algebra sets intrinsic time scales and makes minimal times positive. → Quantum controllability, Quantum speed limits
- Dynamical decoupling
- Sequences of fast pulses that average the coupling between a system and its environment to zero, protecting the system from slow noise. → Dynamical decoupling
- Ensemble (simultaneous) control
- One control that steers a whole family of systems, which differ in an unknown or inhomogeneous parameter, to their targets at the same time — the mathematical basis of robust pulses. → Robust & ensemble optimal control
- Figure of merit
- The quantity an optimal control problem maximizes or minimizes — a fidelity, an expectation value, an error — often combined with costs on the control or the time. → Problem formulation & figures of merit
- Filter function
- A function of frequency that measures how strongly a given control sequence lets noise at each frequency affect the system; the error is, to leading order, its overlap with the noise spectrum. → Filter functions & noise-tailored control
- Floquet engineering
- Designing an effective time-independent Hamiltonian by driving a system periodically, using Floquet theory and high-frequency expansions. → Floquet engineering & periodic driving
- GKSL (Lindblad) equation
- The general form of a Markovian master equation, \(\dot\rho = -i[H,\rho] + \sum_k \big(V_k\rho V_k^\dagger - \tfrac12\{V_k^\dagger V_k,\rho\}\big)\), named after Gorini, Kossakowski, Sudarshan and Lindblad. → Control of open quantum systems
- GOAT
- Gradient Optimization of Analytic conTrols: exact gradients for controls given by analytic functions, obtained by integrating the equations of motion of the propagator’s derivatives. → GOAT
- GRAPE
- GRadient Ascent Pulse Engineering: piecewise-constant controls, with the gradient of the figure of merit with respect to every time slice computed from one forward and one backward propagation. → GRAPE
- Krotov's method
- An iterative method that updates the whole control sequentially in time and is constructed to improve the figure of merit monotonically at every iteration. → Krotov's method
- Leakage
- Population leaving the computational subspace, for example to the third level of a transmon. → DRAG & leakage suppression, Superconducting circuits
- Lie algebra rank condition
- A finite-dimensional closed system is controllable on \(SU(N)\) if the Lie algebra generated by \(iH_0\) and the \(iH_k\) is \(\mathfrak{su}(N)\) (or \(\mathfrak u(N)\)). → Quantum controllability
- Measurement-based feedback
- Control that uses the outcomes of measurements, typically continuous weak measurements processed by a quantum filter, to choose the next action. → Measurement-based feedback
- Piecewise-constant control
- A control that is constant on each of a finite number of time slices — the standard parametrization of GRAPE and the natural output of arbitrary waveform generators. → Pulse parametrization & constraints, GRAPE
- Pontryagin's maximum principle
- Necessary conditions for optimality: an optimal control maximizes a pseudo-Hamiltonian built from the state and a costate that evolves backwards in time. It is the basis of time-optimal and geometric control. → Pontryagin's maximum principle
- Quantum speed limit
- A lower bound on the time needed for a quantum evolution or a control task. In optimal control it is often the minimal time below which a target cannot be reached with the available controls. → Quantum speed limits
- Reachable set
- All states (or operations) that can be reached from a given initial condition with admissible controls, in a fixed time or in any time. → Quantum controllability
- Reservoir engineering
- Designing the coupling of a system to an environment so that dissipation itself drives the system to a desired state. → Reservoir engineering & dissipative preparation
- Rotating-wave approximation
- Neglecting rapidly oscillating counter-rotating terms in a driven system, valid when the drive is weak and close to resonance. → Problem formulation & figures of merit
- Shortcuts to adiabaticity
- Protocols that reach the result of a slow adiabatic process in a much shorter time — by counterdiabatic driving, invariant-based inverse engineering or related methods. → Shortcuts to adiabaticity
- STIRAP
- Stimulated Raman adiabatic passage: complete population transfer in a three-level system through a dark state, using a counter-intuitive order of two pulses. → Adiabatic passage
- Time-optimal control
- Reaching a target in the shortest possible time with bounded controls or under fixed couplings; its solutions are often bang-bang or singular arcs of Pontryagin’s principle. → Geometric & time-optimal control, Quantum speed limits
- Trap
- A control that is a local but not a global optimum of the figure of merit; a local optimizer started near it stops there. → Control landscapes
Timeline
A selection of milestones, each with the paper it refers to.
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1950
Hahn observes the spin echo — refocusing of dephasing by a pulse, the ancestor of dynamical decoupling.
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1954
Carr and Purcell introduce trains of refocusing pulses; Meiboom and Gill’s modification (1958) makes them robust.
Effects of Diffusion on Free Precession in Nuclear Magnetic Resonance Experiments Phys. Rev. 94, 630-638 (1954) doiModified Spin-Echo Method for Measuring Nuclear Relaxation Times Review of Scientific Instruments 29, 688-691 (1958) doi -
1979
Levitt and Freeman use a composite pulse for robust population inversion in NMR.
NMR population inversion using a composite pulse Journal of Magnetic Resonance (1969) 33, 473-476 (1979) doi -
1983
Huang, Tarn and Clark study the controllability of quantum-mechanical systems with Lie-algebraic methods.
On the controllability of quantum-mechanical systems Journal of Mathematical Physics 24, 2608-2618 (1983) doi -
1985
Tannor and Rice propose controlling the selectivity of chemical reactions by timing pulse sequences.
Control of selectivity of chemical reaction via control of wave packet evolution The Journal of Chemical Physics 83, 5013-5018 (1985) doiCoherent pulse sequence induced control of selectivity of reactions: Exact quantum mechanical calculations The Journal of Chemical Physics 85, 5805-5820 (1986) doi -
1986
Brumer and Shapiro propose coherent control through the interference of excitation pathways.
Control of unimolecular reactions using coherent light Chemical Physics Letters 126, 541-546 (1986) doi -
1988
Peirce, Dahleh and Rabitz formulate optimal control theory for quantum-mechanical systems.
Optimal control of quantum-mechanical systems: Existence, numerical approximation, and applications Phys. Rev. A 37, 4950-4964 (1988) doi -
1992
Judson and Rabitz propose closed-loop learning control — “teaching lasers to control molecules”.
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1998
Feedback-optimized femtosecond pulses control a chemical reaction in the laboratory; in NMR, Glaser et al. determine the largest signal that unitary control of spin ensembles can achieve.
Control of Chemical Reactions by Feedback-Optimized Phase-Shaped Femtosecond Laser Pulses Science 282, 919-922 (1998) doiUnitary Control in Quantum Ensembles: Maximizing Signal Intensity in Coherent Spectroscopy Science 280, 421-424 (1998) doi -
1999
Viola, Knill and Lloyd formulate dynamical decoupling of open quantum systems.
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2001
Khaneja, Brockett and Glaser derive time-optimal controls for coupled spins with geometric methods.
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2003
Palao and Kosloff extend optimal control to unitary transformations — quantum gates.
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2004
Rabitz, Hsieh and Rosenthal argue that quantum control landscapes are generically free of traps.
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2005
Khaneja et al. introduce GRAPE for NMR pulse design.
Optimal control of coupled spin dynamics: design of NMR pulse sequences by gradient ascent algorithms Journal of Magnetic Resonance 172, 296-305 (2005) doi -
2007
Uhrig finds the optimal pulse timing for protecting a qubit from dephasing.
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2009
DRAG pulses suppress leakage in superconducting qubits; optimal control is pushed to the quantum speed limit; transitionless driving is formulated.
Simple Pulses for Elimination of Leakage in Weakly Nonlinear Qubits Phys. Rev. Lett. 103, 110501 (2009) doi -
2010
Shortcuts to adiabaticity are introduced for fast frictionless cooling of atoms in traps.
Fast Optimal Frictionless Atom Cooling in Harmonic Traps: Shortcut to Adiabaticity Phys. Rev. Lett. 104, 063002 (2010) doi -
2011
The CRAB method makes optimal control practical for many-body dynamics.
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2015
The first European roadmap for quantum optimal control is published.
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2018
GOAT gives exact gradients for analytic controls; reinforcement learning is applied to quantum control.
Tunable, Flexible, and Efficient Optimization of Control Pulses for Practical Qubits Phys. Rev. Lett. 120, 150401 (2018) doi -
2022
The updated European roadmap for quantum optimal control in quantum technologies is published.
Quantum optimal control in quantum technologies. Strategic report on current status, visions and goals for research in Europe EPJ Quantum Technol. 9, 19 (2022) doi -
2025
QCPOP finds globally optimal controls with polynomial optimization.
Globally optimal control of quantum dynamics Phys. Rev. Research 7, 043202 (2025) doi · arXiv:2209.05790