Quantum Control in the Era of Quantum Computing...Alicia B. Magann DOE CSGF Program Review July,...

Alicia B. Magann July, 2021DOE CSGF Program Review

Alicia B. Magann, Matthew D. Grace, Mohan Sarovar, Herschel A. Rabitz

Princeton University Sandia National Laboratories

Quantum Control in the Era of Quantum Computing

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525


Designing photonic reagents is hard - so far only proof-of-principle demonstrations in experiments

“photonic reagent”

Lasers can create tailored light to control chemical transformations that would not otherwise be possible

• selective bond-breaking

• molecular orientation• molecular rearrangement

• etc…

Progress is limited by the computational difficulty of simulation support

This Talk: Quantum computing for enabling chemistry with photonic reagents

quantum dynamics

• isotope selective processes• charge and energy transfer

Controlling chemistry with light


Classical Computer

Create Experiment

Quantum Device

MeasureUpdate

Cost functional optimization

Cost functional evaluation

(a) Pulse level (b) Circuit level

QOC VQA

Ut[{fk(t)}] = T e�iR t0 dt

0H[{fk(t0)}] U({✓i}) =

Y

i

Ui({✓i})

Update to improve control performance

Evaluate control performance

experiment computer

0 01

quantum computer

InfeasibleInfeasibleCurse of

dimensionality

Quantum optimal control


Quantum computingClassical computing: store information in bits

which can be 0 or 1, do logical operations on these bitsQuantum computing: store bits in

the state of a quantum object - “qubits”

0 010 00

Initialization Computation Readout

Prepare qubits in a specified initial state

Apply a sequence of gates to the qubits in order to perform computation

Measure the qubits to read out the results of the computation

Landmark papers from 1990’s showing quantum speedup for factoring, quantum simulation, unstructured search

Worldwide engagement in developing these quantum computing capabilities

Today:Intense interest in hybrid

quantum-classical algorithms


Computation0 00Initialization

0 01Readout

J({θi})

J({θi}(k)){θi}(k)

φ

AB Magann, MD Grace, HA Rabitz, M Sarovar, Phys. Rev. Research 3, 023165 (2021)

Hybrid quantum/classical algorithm for quantum optimal

control



0 01Readout

J({θi})

J({θi}(k)){θi}(k)

φ

• Define objective function that quantifies how well control target is achieved

J({θi})

• Define model for chemical system and laser light parameterization

• Define control target



control


J({θi}(k)){θi}(k)


0 01Readout

J({θi})φ



control


J({θi}(k)){θi}(k)


0 01ReadoutEncoding our model into qubits provides

exponential memory savings

J({θi})φ


qubits𝒪(M log(d)) bits𝒪(dM)

degrees of freedom represented using

dimensions each

Md


control



0 01Readout

J({θi}(k)){θi}(k)

J({θi})φ



control


J({θi}(k))


0 01Readout

S Lloyd, Science 273, (1996).

{θi}(k)

J({θi})φ

Simulating quantum dynamics using a quantum circuit provides exponential

runtime savings



control

Alicia B. Magann July, 2021DOE CSGF Program ReviewSlide 5

J({θi})


AB Magann, MD Grace, HA Rabitz, M Sarovar, arXiv:2002.12497 (2020)

J({θi})φ


control

https://arxiv.org/abs/2002.12497

https://arxiv.org/abs/2002.12497



controlComputation

0 00Initialization

0 01Readout

J({θi}(k)){θi}(k)

J({θi})φ



Controlled excitonic state preparation in light harvesting

complex

Consider controlling the preparation of an excitation on the second chromophore

Model: S. Hoyer, et al, New J. Phys 16, 045007 (2014).

Model for portion of FMO complex of green sulfur bacteria


(a)

(b)

(c)

0 010 00


Trout, Colin J., et al. New Journal of Physics 20.4 (2018): 043038.

Errors Errors Errors

Current quantum computers are not only limited by size or speed, but also by errors

Controlled excitonic state preparation in light harvesting

complex (a)

(b)

(c)

J(θ 1

,θ2)

θ 2

θ1

We numerically explored the feasibility of meaningful implementation on error-prone trapped ion quantum hardware


Summary• Quantum optimal control simulations involving molecular systems are notoriously challenging

• The advent of quantum computing has the potential to enable simulations of controlled molecular dynamics in polynomial time

• Curse of dimensionality

• This talk introduced a hybrid quantum-classical algorithm for designing optimal laser fields for controlling molecular dynamics

• Explored applications to state preparation in light harvesting complexes• Performed feasibility study for algorithm implementation on near-term quantum computers


Thank you “If you want to make a simulation of Nature, you’d better make it quantum mechanical”

Richard Feynman

Matthew Grace

Mohan Sarovar

Herschel Rabitz

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525

Quantum Control in the Era of Quantum Computing...Alicia B. Magann DOE CSGF Program Review July,...

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