Sergi Ramos successfully defends his undergraduate project TFG at UB

Last July, BSC member Sergi Ramos defended his TFG (Treball de Final de Grau, the equivalent of a Bachelor’s thesis) titled ‘Gap analysis for an adiabatic approach to the Exact Cover problem’. Sergi received an outstanding score!

Here is a summary of the project:

Adiabatic quantum computation is widely used for solving satisfiability problems. One of this problems is the Exact Cover problem, an extension to the 3-SAT problem with a unique solution. This fact makes the adiabatic approach to quantum computation extremely useful when solving this Exact Cover problem, as one can map the unique solution to a non-degenerate energy ground state.

The time needed to perform a computation scales with the inverse of the gap energy, squared. This gap energy is the energy difference between the ground state, solution of the problem, and the first excited state. A way in which the computation time can be improves is by finding an algorithm that increases the gap energy of the problem.

The algorithm proposed is based on the idea that not all clauses of the problem affect the outcome in the same way. Using a weighted system that classifies each clause in the problem using their number of appearances in each different instance, an improvement in the gap energy has been found. Additionally, the gap gain increases with the number of clauses (qubits) in the problem, since their underlying symmetries can be exploited more easily.

Congratulations Sergi!!

Improvement provided by Sergi’s algorithm, seen as a higher slope towards large n than linear.

QUANTIC member Pol Forn-Díaz is interviewed at El Confidencial

The QUANTIC team keeps making noise in the media. Today, an article out of an interview by Dr. Pol Forn-Díaz has been published at El Confidencial. In the article, Pol describes with rather high accuracy the techniques used to fabricate devices, and explains with a dose of realism what building a quantum processor entails. The article also refers to Pol’s PhD advisor Prof. Mooij at TU Delft, as one of the fathers of one of the most important superconducting qubits, the flux qubit.

It is true Pol was the first in the country to learn about the fabrication and measurement techniques of superconducting qubits. By now he is not the only one, but he is one of the very few active and the only one leading an experimental team at a research institute such as BSC.

Pol posing in front of the ICN2 dilution fridge which is being wired up for the first superconducting qubit experiments in the country.

1st Benasque Summer School on Experimental Quantum Computation

The first Benasque Summer School on Experimental Quantum Computation took place from July 10th-July21st. It was a great success of participation. A young generation of experimentalists and theorists met with experts in the world of several of the most advanced areas to implement quantum computation:

Superconducting qubits (Rami Barends, Google)

Quantum dots in semiconductors (Hendrik Bluhm, Aachen)

Ion traps (Philipp Schindler, Innsbruck)

Photonic circuits (Geoff Pryde, Grittifh University)

Donors in silicon (John Morton, University College London)

Adiabatic Quantum Computation and online quantum computers (Alejandro Perdomo-Ortiz, Rigetti Computing)

Theory of Quantum Computation (José Ignacio Latorre, BSC-UB).


Happy birthday QUANTIC!

The QUANTIC group gathered last week to celebrate its first year of existence. A lot has been achieved and a lot needs to be done. Year 2 will bring lots of interesting times and lots of entangled qubits. Stay tuned!

First QUANTIC-only paper!

The QUANTIC group has produced the first work on by QUANTIC-only members, Artur Garcia-Saez and Jose Ignacio Latorre, on one of the main research directions of the team: quantum algorithms! The manuscript reference is arxiv:1806.02287

In this work the focus is on improving the performance of the nowadays popular variational quantum eigensolvers, or VQE. These algorithms are hybrid in that they have a classical part and a quantum part. The classical part consists of optimization methods which then influence the parameters of a quantum circuit that eventually produces an estimation of a certain parameter. This parameter is then important to calculate binding energies of molecules, for instance. This is actually one of the most promising real-life problems which quantum computers, even the noisy, small-scale ones existing these days.

With the new algorithm designed in this work, the Adiabatically-Assisted Variational Quantum Eigensolver (AAVQE) a modification of usual VQE is introduced, in which one starts from a trivial Hamiltonian that produces an exact estimation of a certain parameter. This feeds in a second step in which the Hamiltonian is slightly less trivial. Eventually one arrives at the real-problem Hamiltonian but with a set of parameters evolved in such a way that the result of the problem is obtained directly. In their wok, Artur and José Ignacio have been able to show that the AAVQE algorithm works very well for classical problems, unlike the usual VQE, as has been recently stated.

An instance of the AAVQE algorithm in action.


Alba Cevera-Lierta awarded IBM ‘Teach me QISKit’

We are very happy to announce that our PhD student Alba Cervera-Lierta has won the IBM Q “Teach me QISKit’ by IBM” award! The contest was about writing and programming an interactive self-paced Jupyter Notebook tutorial that explained a specific focus topic in quantum computing using QISKit and the IBM Q Experience.
QISKit is an open quantum software developer toolkit provided by IBM Q to program quantum algorithms, both using a simulator or on one of their quantum devices.
Alba has programmed a quantum circuit that diagonalizes exactly the one-dimensional transverse Ising model. This model shows a quantum phase transition when the transverse magnetization reaches a critical point. At that point, the expected value of magnetization jumps due to the paramagnetic-ferromagnetic spin transition.
The quantum circuit, first proposed by Vestraete, Cirac and Latorre in 2008, has potential interests in condensed matter physics as it allows the exact simulation of all energy spectrum. Thus, other interesting simulations could be performed: for instance, Alba presented the time evolution of the state with all spins aligned, which shows an oscillation in the magnetization.
Finally, we just want to congratulate our collaborator for a job well done!
Enhorabona Alba!


QUANTIC group turns 1

Exactly a year ago, on June 1st 2017, we embarked in this adventure starting from a shared office at UB. We have gone a long way. Our team has grown in size, we have become a reference group for the community, we organized local and international events, we published relevant works in quantum computing and quantum optics, and we have an experiment about to be launched with one of the many collaborators we consolidated. But we are just getting started.

The coming year is going to consolidate our efforts theoretically and experimentally. We will show the first functional superconducting qubit in the south of Europe, new algorithms… but let’s not get ahead of the most important moment: the present. We have big news to celebrate (see next post), while we prepare the first experimental Benasque summer school and a lot more to come! Stay tuned!

Medium posts by Alba Cervera-Lierta

QUANTIC team member Alba Cervera-Lierta has begun a series of pedagogical posts about quantum technologies on the Medium channel of the Quantum World Association.

In the first post titled ‘Quantum Computation: playing the quantum symphony’, Alba gave a nice introduction to qubits and the existing market of quantum technologies. At the end of the post, a beautiful figure classifies all existing businesses around quantum technologies. Such a figure already had a lot of attention by the media and the community.

New review article by Dr. Forn-Díaz

A new article has been completed by QUANTIC group member Pol Forn-Díaz. The review titled ‘Ultrastrong coupling regimes of light-matter interaction’ is a compilation of the evolution of this area in quantum optics exploring the boundaries of the field. Dr. Forn-Díaz has been a pioneer with his PhD as well as postdoctoral work with superconducting qubits coupled to resonators and open systems. The review includes an overview of the history of the Rabi model since its inception, and includes progress in other relevant experimental areas such as polaritons in semiconducting microcavities and other hybrid systems such as molecules in cavities and magnons in microwave resonators.

This work is a collaboration with members of the UPV Bilbao group from Enrique Solano, Lucas Lamata and Enrique Rico, as well as Prof. Jun Kono from the Rice University at Houston, in Texas.

The article has been posted on the arxiv repository with reference 1804.09275.

Figure from the review containing a summary of the main results in different areas with maximum coupling strength normalized to the cavity mode.

Official presentation of MIT-La Caixa Seed Fund project

Dr. Pol Forn-Díaz from the QUANTIC team participated in the press release of the MIT-La Caixa Seed Fund project at the beautiful Palau Macaya in Barcelona. The project titled ‘Multi-Qubit Couplings in Superconducting Quantum Circuits’ involved a collaboration with Prof. W. D. Oliver at MIT.

The event was led by Àngel Font (La Caixa), Mercè Balcells (MIT, IQS and one of the instigators of this seed fund), and awardees Josep Samitier (director of IBEC) and Alexandra Muñoz Bonilla (IMDEA). The fund has awarded a total of 12 projects out of the 30 which were evaluated. BSC obtained two awarded projects. See the BSC press release for more information.

The news was picked up by the media. You can read the news on the official La Caixa foundation site (in Spanish/Catalan), newspapers Ara (Catalan), La Vanguardia (Spanish), El País (Spanish), El Mundo (Spanish).