Qubitserf

Distance finder for quantum codes.

Disclaimer: this code is still very much in early-development, but its main functionality is mostly considered to have been achieved.

Build instructions

Call the script compile.py. You will find the generated files in the build folder, most importantly the executable interface.

Use instructions for the interface

The program uses a meet in the middle algorithm by default which uses $\mathcal{O}(n^{\lfloor d/2 \rfloor})$ memory, where $n$ is the number of qubits and $d$ is the distance of the code. Add the stabilizers line by line as in the example below. The input is considered complete upon reading an empty line or EOF.

When the input is a CSS code

Run using the flag --zx for the program to output both the $Z$-distance and the $X$-distance.

If one wants to compute the distance using the Brouwer-Zimmerman algorithm (constant memory use, parallelizable) instead of the default, call the interface using the --bz flag; if you wish to parallelize the computation, use the --threads flag, followed by maximum number of threads to break the process into.

When the input is not a CSS code

There are no flags to use.

Example interactions

In the following example, a large CSS code is provided as input and the program outputs 5 4, meaning that the code has $Z$-distance $5$ and $X$-distance 4. It also lets the program break the task into 16 threads.

./interface --bz --zx --threads 16
ZZIIIZZIIIIIIIIIIIII
IXXIIIXXIIIIIIIIIIII
IIZZIIIZZIIIIIIIIIII
IIIXXIIIXXIIIIIIIIII
IIIIIXXIIIXXIIIIIIII
IIIIIIZZIIIZZIIIIIII
IIIIIIIXXIIIXXIIIIII
IIIIIIIIZZIIIZZIIIII
IIIIIIIIIIZZIIIZZIII
IIIIIIIIIIIXXIIIXXII
IIIIIIIIIIIIZZIIIZZI
IIIIIIIIIIIIIXXIIIXX
XXIIIIIIIIIIIIIIIIII
IIXXIIIIIIIIIIIIIIII
IIIIIIIIIIIIIIIXXIII
IIIIIIIIIIIIIIIIIXXI
IIIIIZIIIIZIIIIIIIII
IIIIZIIIIZIIIIIIIIII
IIIIIIIIIIIIIIZIIIIZ

5 4

In the following example, a large CSS code is provided as input and the program outputs 4, meaning that the code has distance 4.

./interface
ZZIIIZZIIIIIIIIIIIII
IXXIIIXXIIIIIIIIIIII
IIZZIIIZZIIIIIIIIIII
IIIXXIIIXXIIIIIIIIII
IIIIIXXIIIXXIIIIIIII
IIIIIIZZIIIZZIIIIIII
IIIIIIIXXIIIXXIIIIII
IIIIIIIIZZIIIZZIIIII
IIIIIIIIIIZZIIIZZIII
IIIIIIIIIIIXXIIIXXII
IIIIIIIIIIIIZZIIIZZI
IIIIIIIIIIIIIXXIIIXX
XXIIIIIIIIIIIIIIIIII
IIXXIIIIIIIIIIIIIIII
IIIIIIIIIIIIIIIXXIII
IIIIIIIIIIIIIIIIIXXI
IIIIIZIIIIZIIIIIIIII
IIIIZIIIIZIIIIIIIIII
IIIIIIIIIIIIIIZIIIIZ

4

To do:

• Write a python wrapper
• Implement the dynamic Brouwer-Zimmerman algorithm
• Enable GPU acceleration for the exponential part
• $$$$$$