David López and his outreach

The Quantic member David lópez Núñez took part in the “Nit de Recerca Jove (European Researchers’ Night) 2019” hosted by CSIC, and gave a talk in his former High School in L’Hospitalet de Llobregat.

The title of the talks was: “Bricocuántica, ¿Cómo hacer un ordenador cuántico?” (Quantum DIY: how to make a quantum computer?)

      

 

It is always nice to get closer to new generations! Good job!

Our students this year (II)

The last of Quantic students, Rafael Luque, has presented his work with great results. Below one can find the updated list of grades

Bachelor:

Gabriel Fernández: Quantum Autoencoders; 8,6

Elies Gil: Variational Quantum Classifier; 9,7

Josep Lumbreras: Scaling of the energy and entropy errors in quantum circuits; 9,1

Santi Vallés: Design of infrared filters to improve the quality of a superconducting qubit; 9,3

Master:

Sergi Ramos: Maximal Entanglement in One-Loop Z Boson Decay; 9,1

Rafael Luque: Coherent control of a superconducting quantum bit; 9

 

Everyone did a great job at Quantic. Some of them will continue within the team, other people will spread their wings. The best of luck for you all!

New article by group’s member

PhD student Carlos Bravo-Prieto posted a pre-print article as the result of his summer stay at Los Álamos (NM, USA):

“Variational Quantum Linear Solver: A Hybrid Algorithm for Linear Systems”, by C. Bravo-Prieto (), R. LaRose (), M. Cerezo (), Y. Subasi, L. Cincio and P. J. Coles (). preprint:

In this work, they presented a variational quantum algorithm for solving the quantum linear system problem. On the analytical side, they derived efficient quantum circuits to estimate faithful cost functions, while showing that they are difficult to estimate classically.

Schematic of the quantum linear solver algorithm.

On the numerical side, they studied the scaling of the algorithm run time and found it to be efficient with respect to the condition number and the desired precision:

Furthermore, they implemented the variational algorithm in ‘s quantum computer, for particular problems up to a size of 32×32, which is the largest implementation of a linear system on quantum hardware:

We have a new PhD student!

This September a new PhD student will join the Quantic group. Sergi Ramos, who has already worked with us in his TFG (Treball de Fi de Grau) and TFM (Treball de Fi de Màster) will be from now on a member of the theory division of the group.

We know we have signed up a good researcher. Welcome (again) Sergi!

Our students this year

As the summer ends, we show here the Bachelor’s and Master’s theses our students have presented this year

Bachelor:

Gabriel Fernández: Quantum Autoencoders; 8,6

Elies Gil: Variational Quantum Classifier; 9,7

Josep Lumbreras: Scaling of the energy and entropy errors in quantum circuits; 9,1

Santi Vallés: Design of infrared filters to improve the quality of a superconducting qubit; 9,3

Master:

Sergi Ramos: Maximal Entanglement in One-Loop Z Boson Decay; 9,1

Rafael Luque: Coherent control of a superconducting quantum bit; 9

 

Everyone did a great job at Quantic. Some of them will continue within the team, other people will spread their wings. The best of luck for you all!

Quantic turns 2 years old

We are glad to announce that the Quantic family keeps growing. We are already two years old and have more members than ever. Congrats for these two years, and we look forward new and exciting science and projects.

We would like to welcome all new partners to Quantic, and to wish all the best for all people leaving the group. We will see each other again soon.

 

New paper by the Theory team

We present our last article “Data re-uploading for a universal quantum classifier”, by A. Pérez-Salinas, A. Cervera-Lierta, E. Gil-Fuster and J. I. Latorre. It is available in arXiv:1907.02085 and SciRate

 

The main result of this work is to show that there is a trade-off between the number of qubits needed to perform classification and multiple data re-uploading.

The quantum classifier we built can be understood as a modification of a Neural Network. In feed-forward neural networks (NN), each data point is entered and processed in each neuron. If NN were affected by the no-cloning theorem, they couldn’t work as they do. To build a quantum classifier (QClass), we need to load classical data several times along the computation.

To upload and process data in the QClass, we use a general unitary gate. Each of these gates (called “layer L”) introduces the data points “x” and the processing parameters “phi” that should be adjusted by using some cost function.

We train a single-qubit QClass by dividing the Bloch Sphere into several regions, one for each class, and fine-tune the processing parameters to distribute each data point to its corresponding region. We choose these regions to be maximally orthogonal.

Then, we can define the cost function as the fidelity of the final state of the QClass and the corresponding “class state”. We propose two ways to do that, which can be found in the article. A single-qubit QClass can’t represent any quantum advantage, although, for its simplicity, could be a part of larger circuits. However, this QClass can be generalized to multi-qubit QClass, where the introduction of entanglement will improve the classification procedure. Once we have defined the QClass and the cost function, we need to use a classical minimization method to find the processing parameters. The QClass belongs to the family of parametrized quantum circuits, as the VQE or Qautoencoder. We have used the L-BFGS-B algorithm from scipy.

Benchmark: we have tested the single- and multi-qubit QClass composed by a different number of layers in several problems with different characteristics.

 

New Doctor at Quantic!

We are glad to announce that last June 21st the member of Quantic Alba Cervera-Lierta has become the first Quantic doctor. She defended her PhD thesis in front of Dr. Alejandro Perdomo-Ortiz (Zapata Computing Inc.), Dr. Ivano Tavernelli (IBM-Zürich) and Prof. Germán Sierra (IFT-CSIC).

The whole Quantic Group congratulates you. Your amazing perseverance as well as your dedication has at last paid off.

Congrats, Alba! There is a wonderful future ahead of you!

 

 

Experimental team moves to IFAE

Since May 1st 2019, the experimental team in Quantic led by Pol Forn-Díaz is now located at the High Energy Physics Institute (IFAE, Institut de Física d’Altes Energies), located at the UAB campus in Bellaterra, near Barcelona.

The move represents the first time IFAE gets involved in quantum computation, joining in this way BSC and UB within the QUANTIC family. IFAE has traditionally focused its research in particle detection, both at accelerators as well as those with cosmic origin. It also develops X-ray detection for medical purposes, neutrinos, and more recently gravitational waves. The electronics and mechanical workshops are world-class and will be extremely positive for the development of the experimental team at Quantic.

Pol Forn-Díaz has established the Quantum Computing Technology group at IFAE, being the PI of this new line of research. One of the other PIs at IFAE, Prof. Manel Martínez who led the creation of the MAGIC consortium and now leads the CTA project on gamma-ray astronomy, is joining the Quantic team, strengthening the experimental side significantly.

The rest of the experimental team in QUANTIC is also moving to IFAE. All IFAE members will retain the BSC affiliation through an institutional agreement signed between the two centers.

New publication by Dr. Forn-Díaz

The review article by Dr. Forn-Díaz and co-workers from Bilbao and Huston titled “Ultrastrong coupling regimes of light-matter interaction” has finally been published in the prestigious journal Reviews of Modern Physics.

This article reviews the state of the field in the regime in which light and matter interact so strongly that the whole system becomes a new entity with exotic properties. The review particularly focuses on the experimental progress in the last decade on the fields of superconducting qubits coupled to microwave photons and polaritons in semiconductor quantum wells coupled to infrared radiation. This field keeps gathering interest due to its fundamental intricacies (recent works studying the gauge invariance is just one more example), and the potential to find applications in quantum technologies. In fact, Dr. Forn-Díaz is leading a proposal for a European call to fund a project on ultrastrong couplings and quantum technologies.

The landmark of the review is the evolution of the coupling strength normalized to the bosonic mode frequency over time and for many fields. Clearly, experiments have finally managed to enter the USC regime just very recently, and a whole new field is ready to be explored.

Plot of reduced light-matter coupling strength over time for several different fields.