Quantum Photonic Simulation of Molecular Spectra

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics

Abstract

Project summary: We will develop a quantum-enhanced simulator of molecular vibronic spectra, based on the interference of quantum light. Photonic processing capabilities are currently far from meeting the stringent requirements for universal quantum computation; however, photonics does provide unique, and powerful, approaches to limited-purpose processors. For example, the Boson Sampling (BS) computing problem, which concerns the statistics of single photons exiting a multi-port interferometer, is recognized as a promising framework for the experimental demonstration of quantum supremacy in computing. The project we propose here builds on a BS variation that identifies a connection to molecular transitions, recently put forth by Alán Aspuru-Guzik (Harvard) and collaborators (10.1038/nphoton.2015.153). In this scheme, the interference of quantum light naturally emulates the electronic-vibronic transitions in complex molecules. The statistics from such an interferometer will reveal the spectrum of the molecule- a key task in theoretical chemistry that is currently limited by the power of classical computation.
This student project aims to achieve the first demonstration of this type of simulator. We will also develop a theoretical connection of the simulator to Gaussian Boson Sampling, clarify the consequences of experimental imprecision, and formulate a route to molecule simulation that will surpass the current capacity of classical computation.
This project falls within the EPSRC Quantum Technologies research area, as it is one of the studentship projects associated with the NQIT Hub. The impact of this project will include its contribution toward NQIT goals: building a photonic simulator is NQIT deliverable D23 (Month 58). In current plans, this consists of a large-scale BS machine (based on the "scattershot" variation) and a small-scale co-processor for DMFT calculation (with the quantum simulation research group in NQIT). The proposed device is a new concept fr a photonic simulator. If successful, this device would have impact beyond the academic race to quantum supremacy by connecting the computational promise of BS to a task of wide interest in chemistry and molecular biology.
One full-time NQIT researcher is working towards the photonic simulator. To date, this has primarily involved developing technical components for the simulator through collaborative projects with researchers working on non-NQIT projects. The proposed project aligns closely with this ongoing work, and critically, it provides a dedicated researcher needed to investigate this promising new concept.
The molecular simulator is an example of a purpose-built quantum processor that runs without error correction. The photonic simulator will stimulate NQIT activity in this type of computation, which is likely to be the first achieved at an interesting scale with an NQIT ion-trap processor. Important theoretical problems to investigate with NQIT researchers include verification and error tolerance. The technical requirements to build the simulator have complete overlap with the light sources, interferometers, and detectors developed and used for other aspects of NQIT photonics. Beyond NQIT, we will collaborate with Aspuru-Guzik to compile a test set of molecules that are interesting from the perspective of a computational chemist, and understand how a realistic environment (e.g. collisions in solution) is simulated by optical loss and dephasing.

Publications

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publication icon
Sperling J (2020) Detector-Agnostic Phase-Space Distributions. in Physical review letters

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509711/1 01/10/2016 30/09/2021
1796891 Studentship EP/N509711/1 01/10/2016 08/04/2020 David Phillips
 
Description The outcomes of this award are a little different to what was originally set, though still with relevance and on the same topic. First, we explored a benchmarking protocol for Gaussian Boson Sampling, something which I wrote about in last year's submission. Gaussian Boson Sampling is the procedure required for Quantum Photonic Simulation of Molecular Spectra, and thus benchmarking is an important experimental consideration. Our benchmarking procedure was able to distinguish between Gaussian Boson Sampling and the classical analogy.

Some additional work done under this award includes Weak Field Homodyne Detection. In this project we demonstrated the transition between a non-Gaussian measurement and a Gaussian measurment on Gaussian optical states. The non-Gaussian measurement on Gaussian states is equivalent to Gaussian Boson Sampling. The work done in this project is important for state characterisation and engineering. Additionally, we used a variant of this experimental setup to measure arbitrary phase-space distributions wich work for a variety of detector models.
Exploitation Route The outcomes of this funding could be used for diagnostic and characterisation purposes for Quantum Photonic Simulation of Molecular Spectra. They could be used as a diagnostic tool for infrastructures, and for photonic state characterisation. Also some experimental components are relevant, such as the photonic sources and photon-number resolving detectors.
Sectors Chemicals,Digital/Communication/Information Technologies (including Software),Healthcare,Pharmaceuticals and Medical Biotechnology

URL https://arxiv.org/abs/1908.04765
 
Description There is a startup in Canada called Xanadu who work in the field of continuous variable quantum computing. They are interested in a publication I was first author on as it discusses a benchmarking scheme they could implement on their products.
First Year Of Impact 2019
Sector Digital/Communication/Information Technologies (including Software),Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Benchmarking of Gaussian Boson Sampling 
Organisation Sorbonne Universit├ęs
Country France 
Sector Academic/University 
PI Contribution We worked together on a theory project, here we focused more on simulations and experimental applications.
Collaborator Contribution Our collaborators focused more on the theoretical framework of the project.
Impact We published an article on our findings.
Start Year 2018
 
Description Building Large Optical Quantum States 
Organisation Imperial College London
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution At Oxford we have worked on the testing and implementing the technology that our collaborators have provided for us.
Collaborator Contribution Imperial College London - Theory support NIST - manufacture novel photon detection technology Southampton - manufacture on-chip waveguides for photonic manipulation The devices that have been produced for us to test or use were not for commercial purposes (and sometimes not even available comercially), hence why no 'in kind' contributions have been selected since nothing was bought for us.
Impact There have been many publications from this collaboration, but none that I have been directly involved with as of yet.
Start Year 2015
 
Description Building Large Optical Quantum States 
Organisation National Institute of Standards & Technology (NIST)
Country United States 
Sector Public 
PI Contribution At Oxford we have worked on the testing and implementing the technology that our collaborators have provided for us.
Collaborator Contribution Imperial College London - Theory support NIST - manufacture novel photon detection technology Southampton - manufacture on-chip waveguides for photonic manipulation The devices that have been produced for us to test or use were not for commercial purposes (and sometimes not even available comercially), hence why no 'in kind' contributions have been selected since nothing was bought for us.
Impact There have been many publications from this collaboration, but none that I have been directly involved with as of yet.
Start Year 2015
 
Description Building Large Optical Quantum States 
Organisation University of Southampton
Department Optoelectronics Research Centre
Country United Kingdom 
Sector Academic/University 
PI Contribution At Oxford we have worked on the testing and implementing the technology that our collaborators have provided for us.
Collaborator Contribution Imperial College London - Theory support NIST - manufacture novel photon detection technology Southampton - manufacture on-chip waveguides for photonic manipulation The devices that have been produced for us to test or use were not for commercial purposes (and sometimes not even available comercially), hence why no 'in kind' contributions have been selected since nothing was bought for us.
Impact There have been many publications from this collaboration, but none that I have been directly involved with as of yet.
Start Year 2015