## A new paper from the theory team: Quantum Computing in High Energy Physics

Today the paper * Determining the proton content with a quantum computer *by Quantic member Adrián Pérez-Salinas, in collaboration with Juan Cruz-Martinez, Abdulla A. Alhajri and Stefano Carrazza came out (arXiv: 2011.13934)

In this paper they present a first attempt to design a quantum circuit for the determination of the parton content of the proton through the estimation of parton distribution functions (PDFs), in the context of high energy physics (HEP). In this work they identify architectures of variational quantum circuits suitable for PDFs representation (qPDFs) and show experiments about the deployment of qPDFs on real quantum devices, taking into consideration current experimental limitations. Finally, they perform a global qPDF determination from LHC data using quantum computer simulation on classical hardware and they compare the obtained partons and related phenomenological predictions involving hadronic processes to modern PDFs.

The quantum algorithm herein proposed belongs to the class of Variational Quantum Circuits that rely on both quantum and classical resources.

The final Ansatz chosen to create the quantum circuits encoding the qPDFs within can be easily described through a layered structure

There are two different kinds of single-qubit gates serving as building blocks of such circuits, giving raise to the Weighted and Fourier Ansätze

These Ansätze can be used with and without entangling gates to create single- and multi-flavour fits. We consider the flavours

Both Ansätze provide accurate results when we fit some known PDF with them, ensuring a great flexibility for the model with few layers and parameters (the table with lower numbers corresponds to the Weighted ansatz)

Knowing that the model works, they implement it now in actual quantum computers, using the single- and multi-flavour models. For the single-flavour fit they used the IBMQ Athens processor

For the multi-flavour fit, they used simulated versions of IBMQ Melbourne whose errors were under control. The results deteriorates rapidly in this case.

The third step of the work consists in using the quantum model to fit actual PDFs in order to fulfill the requirements provided by LHC data. To do so, they made use of the NNPDF methodology and substituted the Neural Networks (NN) by the quantum model (as a simulator). This procedure provide also satisfactory results for PDF fitting

And returns phenomenology predictions in agreement with state-of-the art PDF fitting.

In conclusion, the qPDF model provides great flexibility and is capable to fit PDFs according to LHC data. This may open the possibility to use quantum computing for this kind of operations. However, current qualities of the quantum computers prevents the immediate implementation, and computational capabilities of this model are not enough yet to compete against modern high-performance NNPDF computations.

## Qibo, a new open source framework for quantum simulation with hardware acceleration

We are very excited to present **Qibo**, the quantum simulator made by some members of Quantic in collaboration with researchers from the Technology Innovation Institute in Abu Dhabi and the University of Milano. The full paper can be read in arXiv, and the source code has been uploaded to GitHub.

Qibo is a new open-source software for fast evaluation of quantum circuits and adiabatic evolution which takes full advantage of hardware accelerators. In this work we introduce a new quantum simulation framework that enables developers to delegate all complicated aspects of hardware or platform implementation to the library so they can focus on the problem and quantum algorithms at hand. This software is designed from scratch with simulation performance, code simplicity and user friendly interface as target goals. It takes advantage of hardware acceleration such as multi-threading CPU, single GPU and multi-GPU devices.

Qibo has plenty of functionalities that will make the work with quantum circuits much user-friendlier (up), as well as some predefined models (down)

Qibo is constructed as a stack with the structure below. This structure allows the software to have a high level API together with some useful algorithms serving as tools to be used by quantum developers. Then, backends and operators, constructed on top of TensorFlow, manage all the processes needed to obtain as much efficiency as possible by specializing operators for CPU and GPU. The abstraction layer performs the operations themselves.

Qibo includes all precision and hardware configurations available for other programming languages in the same package. In addition, switching from one configuration to another is easily done by writing a pair of lines of code. Every configuration is optimal for some conditions.

The performance of Qibo is comparable or superior to previous programming languages for quantum simulation. For an instance of Quantum Fourier Transform (QFT), the best results are obtained for large numbers of qubits. In the case of adiabatic evolution, also great advantages have been achieved.

The future work serving as continuation for this first release of Qibo will include a scheme to send Qibo-jobs to quantum hardware through a remote server and a scheduler. This way, many users will be able to submit their calculations to a quantum processor.

## The hash preimage, a new paper by Quantic members

*Quantum Search for Scaled Hash Function Preimages*has been published in arXiv as a preprint. This is a joint work of S. Ramos-Calderer, E. Bellini, J. I. Latorre, Marc Manzano and Victor Mateu

## Qilimanjaro Quantum Tech SL is established

Recently, some members of QUANTIC have established Qilimanjaro Quantum Tech SL, a new spin-off of our three institutions: the University of Barcelona, Barcelona Supercomputing Center and Instituto de Física de Altas Energías. The PIs of QUANTIC, Dr. José I. Latorre, Dr. Artur Garcia-Saez and Dr. Pol Forn-Díaz, together with experts from the IT and M&A sectors will lead this project.

The future will be Quantum, and Qilimanjaro’s aim is to play an important role in the development of quantum technologies, both in the hardware as in the algorithmic parts. Qilimanjaro will also construct all the structure that is needed to run quantum algorithms in a own-made quantum computer. This quantum hardware will make use of high-quality qubits to perform adiabatic quantum computation. This technique has got enough potential as to offer actual optimization applications in the advent of the quantum era.

This technology will be available in the mean-term future as a cloud service, allowing all users to explore the capabilities of quantum computers.

Do you want to know more? Check out HPC Wire

## Quantic turns 3 years old

Last week Quantic celebrated its third birthday! Although the COVID-19 situation did not let us to hold the full party, as some of the members could not join the event, it is nice to see how the group grows and improves. This last year has been full of surprises, full of news, full of special moments. This has been, as for most of people, a difficult year. However, at the end of the ~~day~~ year, we are allowed to look back and confess: wow, what a year. Cheers to all who made it possible.

The next months promise to be amazing and exciting, great expectations are yet to be fulfilled. Old friends coming and going, new people getting to know us, new projects to accomplish, discoveries hidden ahead of us… Let us hope the future is as brilliant as in our minds.

### Happy Birthday!

## New open postdoc position

The newly established QCT group in Barcelona offers a postdoctoral position within the project SiUCs ( Superinductor-based Quantum Technologies with Ultrastrong Couplings) funded by the European QuantERA program.

The tasks for this position will involve design, fabrication and measurement of superconducting qubit devices coupled to resonator modes to study the physics of this system in regimes of ultrastrong coupling, and its consequences in superconducting-based quantum technologies.

The candidate will closely work in collaboration with the rest of partners in the SiUCs consortium:

- Nicolas Roch (Néel Institute CNRS, Grenoble, FR)
- Ioan Pop (Karlsruhe Institute of Technology, DE)
- Milena Grifoni (Regensburg University, Institute for Theoretical Physics, DE)
- Miroslav Grajcar (Institute of Physics, Slovak Academy of Sciences, SK)
- Elisabetta Paladino (Consiglio Nationale delle Richerche Catania, IT)

Interested candidates are expected to hold a doctoral degree in Physics and must be experienced in experimental superconducting qubit device techniques in at least one of the following areas: quantum optics with superconducting devices, qubit coherent control, quantum simulations with superconducting devices.

Applications should be sent to Pol Forn-Díaz and should include an updated CV with a letter of intent or motivation, and arrange for two or three letters of recommendation. Sending CVs to IFAE implies consent to the legal warning at the bottom of IFAE’s homepage, see the job posting at IFAE’s website.

The appointment will be for a two years term, with the possibility to renew for a third year.

IFAE is an equal opportunity employer committed to diversity in the workplace, and we welcome applications from all qualified candidates. Women are particularly encouraged to apply.

## Great News for our PI

Dear all,

we are glad to announce that the Principal Investigator of Quantic, José Ignacio Latorre, has been selected as the new director of the Center for Quantum Technologies in Singapore. We will join the CQT the next 27th July, taking over from founding director Artur Ekert.

Have the best of lucks in this new opportunity!

## Bojos per la supercomputació

The Quantic members Carlos Bravo-Prieto and David López-Núñez have shared some time with high-school students that are ”crazy for supercomputing”.

First, they have learnt them the basic concepts of quantum mechanics, a necessary step to understand quantum computing, as well as the potential applications of it.

Then, the foundations of quantum computing have been explained, such as how to represent a qubit in the Bloch sphere, (thanks to Quantum Fracture for the nice drawings)

Finally, our students have learnt to simulate quantum algorithms in classical computers.

Hopefully, some of them will join us in the future in this amazing adventure of researching in Quantum Computing. Thank you very much for your attention, and have luck in your brilliant futures!