Pol Forn-Díaz and Alba Cervera-Lierta have participated in European Researchers’ Night 2018 by giving a talk at Cosmocaixa, Barcelona.

They gave a microtalk which consisted on 8 minutes talk about some scientific topic explained to a general audience. First, Alba presented what is a quantum computer and what are its aplications: to study new chemical reactions, to solve optimization problems or to simulate quantum systems. Second, Pol explained how it works and what is the appearence of its building blocks, qubits. In particular, he showed how is our quantum processor made of superconducting qubits.

Quantic team members are very active in scientific outreach activities. Follow us on twitter to stay informed about future events!

Last week we had a distinguished guest for the whole week. Tim Menke from the MIT group of Engineering Quantum Systems visited us through the MIT-La Caixa Foundation project which Dr. Forn-Díaz has together with Prof. Will Oliver from MIT to develop new circuits for quantum annealing and allow students and PIs to spend short periods of time at MIT/BSC.

Tim’s work is focusing on reverse-engineering circuits by theoretically sampling circuits with different properties and selecting the ones that display a response close to the desired one. Then those circuits can be fabricated and tested in an experiment. Tim also performs measurements in the quantum annealing project within MIT.

Tim has helped us a lot in the lab work to get the qubit control electronics and software up and running. Thanks for the visit Tim!

Dr. Forn-Díaz has participated in a joint work with the group of Prof. Chris Wilson at IQC Waterloo on the area of generation of entangled states of microwave generation, which has just been published to Physical Review Applied. The work, part of which was carried out during Pol’s postdoctoral position at Prof. Wilson’s lab, focuses on a nonlinear multimode resonator that generates entangled states of radiation by the application of external pumping fields at the suitable driving frequencies. The key aspect of the circuit is the presence of a SQUID at the end of the line which mediates the interaction between different modes. This work is very important for the generation of nonclassical states of microwave radiation, which are applicable in the area of quantum communication and quantum sensing.

The reference of the publication is Phys. Rev. Applied 10, 044019 (2018).

Quantic group and its team have not passed unnoticed to the media!

For that reason, we have created a new section in Quantic webpage, Media, where we collect everything releated with our group that comes out in the news: interviews, radio podcasts, videos, … You can also check there outreach material written by our team and collaborators.

The Quantic team member Carlos Bravo has been recently awarded with a grant by the Unitary fund from Will Zeng, product lead for the forest experimental quantum programming toolkit at Rigetti Computing, who just started running his own quantum fund.

Carlos’s project will be based on the implementation of Adiabatically Assisted Variational Quantum Eigensolvers (AAVQE) in Forest (Rigetti’s quantum developer environment). This modern classical-quantum algorithm is an original idea from Dr. A. Garcia-Saez and Prof. J.I. Latorre from Quantic and is currently under review (arXiv:1806.02287). The AAVQE tackles optimization problems, with its basic idea being the assistance of variational quantum eigensolvers (VQE) with an adiabatic change of the Hamiltonian. The main problem that VQE algorithms face is in finding a reasonable path in the parameter space of the circuit to ending up in the correct solution. This problem may be solved by adiabatically evolving the Hamiltonian. Finally, Carlos is going to test AAVQE in order to solve hard classic and quantum problems.

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.

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.

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)

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!

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.