Error correction in quantum computers

Theoretical physicists of BME Institute of Physics published new numerical results on the efficiency of the surface code error correction protocol in the journal Quantum.
To perform long computations, the quantum information that quantum computers work on has to be protected against environmental noise. This requires quantum error correction (QEC), whereby each logical qubit is encoded into collective quantum states of many physical qubits. We studied, using numerical simulation, how well the most promising quantum error correcting code, the so-called Surface Code can protect quantum information against a combination of so-called coherent errors (a type of calibration errors) and readout errors. We found that the Surface Code provides better protection as the code is scaled up, as long as the error levels are below a threshold. This threshold is close to the well-known threshold of another combination of errors: incoherent errors (a type of error arising from entanglement with a quantum environment) and readout errors. We also found (as shown in the accompanying image) that the Surface Code is more robust against readout errors than coherent errors. Note that we used the so-called phenomenological error model: we modeled the noise channels very precisely, but did not do a modeling of the code on the quantum circuit level.
Coherent errors and readout errors in the surface code
Áron Márton and János K. Asbóth

Gábor Varga passed away

We are deeply saddened by the loss of our colleague, Dr. Gábor Varga, associate professor of the Department of Physics at the BME Institute of Physics, who passed away unexpectedly at the age of 63.
Gábor worked at the Department of Physics for about 40 years, taught physics to generations of engineering students, and played an important role in the introduction of computer modeling education. He was a highly valued colleague of ours, having strong friendships with many people at the Institute of Physics.
He will be truly missed by his colleagues, who share the pain of Gábor's family. 

Interview with Szabolcs Csonka

Interview with BME's associate professor and Momentum research group leader Szabolcs Csonka published at the news portal of the Hungarian Academy of Sciences. 


The interview:


News item at, in Hungarian:


Website of the MTA-BME Superconducting Nanoelectronics Momentum Research Group:


Physics Prize for Sándor Bordács

Associate professor of BME Institute of Physics received the prize from the Hungarian Academy of Sciences for his outstanding research activities. Congratulations!


Sándor Bordács, head of the Complex Magnetism Research Group of the BME Department of Physics, is an outstanding researcher in modern optics and solid-state physics, advancing the field with creative experiments as well as theoretical models. He has discovered and explained numerous novel optical phenomena, with relevance for optical communication and data storage, acknowledged and highly recognized by the international community of his field. 
Home page of Sándor Bordács:
Home page of the Complex Magnetism Research Group:

Ultra-long spin lifetime in graphite

New experimental results from the BME Institute of Physics, published in Nature Communications, open new perspectives in the spintronics applications of graphite. 


B. G. Márkus, M. Gmitra, B. Dóra, G. Csősz, T. Fehér, P. Szirmai, B. Náfrádi, V. Zólyomi, L. Forró, J. Fabian & F. Simon 
Ultralong 100 ns spin relaxation time in graphite at room temperature
Nature Communications 14, 2831 (2023)