ELFT HÍRADÓ

[Andras Palyi <palyi AT mail.bme.hu>]

Dear Colleagues, 
 
This Friday, our research group at the BME Department of Theoretical Physics 
will host the following online talk:
 
Speaker: Florian Venn (Cambridge)
Title: Error-correction and noise-decoherence thresholds for coherent errors 
in planar-graph surface codes
Reference: https://arxiv.org/abs/2006.13055 <https://arxiv.org/abs/2006.13055>
Time: Aug 7 Friday, 9:15
Location: online in Microsoft Teams (see link below)
 
Abstract: "We numerically study coherent errors in surface codes on planar 
graphs, focusing on noise of the form of Z- or X-rotations of individual 
qubits. We find that, similarly to the case of incoherent bit- and 
phase-flips, a trade-off between resilience against coherent X- and 
Z-rotations can be made via the connectivity of the graph. However, our 
results indicate that, unlike in the incoherent case, the error-correction 
thresholds for the various graphs do not approach a universal bound. We also 
study the distribution of final states after error correction. We show that 
graphs fall into three distinct classes, each resulting in qualitatively 
distinct final-state distributions. In particular, we show that a graph class 
exists where the logical-level noise exhibits a decoherence threshold 
slightly above the error-correction threshold. In these classes, therefore, 
the logical level noise above the error-correction threshold can retain 
significant amount of coherence even for large-distance codes. To perform our 
analysis, we develop a Majorana-fermion representation of planar-graph 
surface codes and describe the characterization of logical-state storage 
using fermion-linear-optics-based simulations. We thereby generalize the 
approach introduced for the square lattice by Bravyi \textit{et al}. [npj 
Quantum Inf. 4, 55 (2018)] to surface codes on general planar graphs."
 
Link to join the meeting in Teams:
https://teams.microsoft.com/l/meetup-join/19%3a897924ab922a49bd9c682451a94eb00d%40thread.tacv2/1596615227713?context=%7b%22Tid%22%3a%226a3548ab-7570-4271-91a8-58da00697029%22%2c%22Oid%22%3a%22f8b27e90-dbca-4bb5-813c-d6415577ec35%22%7d
 
<https://teams.microsoft.com/l/meetup-join/19%3a897924ab922a49bd9c682451a94eb00d%40thread.tacv2/1596615227713?context=%7b%22Tid%22%3a%226a3548ab-7570-4271-91a8-58da00697029%22%2c%22Oid%22%3a%22f8b27e90-dbca-4bb5-813c-d6415577ec35%22%7d>

Best regards,
Andras Palyi