Algorithmic Assertions - Craig Gidney's Computer Science BlogA blog about computer science, software engineering, quantum computing, mathematical puzzles, and so forth.
http://algassert.com
Inverting Clifford Tableaus<p>In quantum computing, the Cliffords are an extremely important class of operations. Cliffords are simple enough to <a href="https://arxiv.org/abs/quant-ph/0406196">simulate</a> <a href="https://arxiv.org/abs/quant-ph/0504117">cheaply</a>, but expressive enough to represent important quantum protocols like error correction and teleportation.</p> <p>A quantum operation $C$ is a Clifford operation if, for any operation $P$ from the Pauli...Sun, 30 Aug 2020 11:10:10 -0700
http://algassert.com/post/2002
http://algassert.com/post/2002Decorrelated Depolarization<p>There are a variety of ways of defining depolarizing errors out there. A common definition, used when analyzing error correction circuits, is that when a depolarizing error occurs to a set of qubits, a random Pauli ($I$, $X$, $Y$, or $Z$) is applied to each qubit. Every combination of Paulis...Tue, 21 Jul 2020 11:10:10 -0700
http://algassert.com/post/2001
http://algassert.com/post/2001[Paper] Compilation of Fault-Tolerant Quantum Heuristics for Combinatorial OptimizationTue, 14 Jul 2020 05:10:10 -0700
http://algassert.com/2020/07/14/paper-compile-optimization.html
http://algassert.com/2020/07/14/paper-compile-optimization.html[Talk at QCTIP2020] How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubitsMon, 06 Apr 2020 09:10:10 -0700
http://algassert.com/2020/04/06/qctip-talk.html
http://algassert.com/2020/04/06/qctip-talk.htmlFactoring the largest number ever with a quantum computer<p><strong>(Update (April 4): I've seen several tweets thinking this post was serious. It's not. Check the publication date.)</strong></p> <p>Ever since Shor's great discovery, quantum computers have been factoring larger and larger numbers. In 2001, the number 15 was factored using 8 qubits. This record was tied many times, but not...Wed, 01 Apr 2020 11:10:10 -0700
http://algassert.com/post/2000
http://algassert.com/post/2000[Talk at Simons Institute] Estimating the Fault Tolerant Cost of Classically Intractable Quantum ComputationsThu, 27 Feb 2020 04:10:10 -0800
http://algassert.com/2020/02/27/simons-talk.html
http://algassert.com/2020/02/27/simons-talk.htmlSurviving Chain Link Erasures<p>An "erasure" is a quantum error where you accidentally lose a qubit (or reset a qubit), but realize that this happened. Erasures are common in quantum computers based on photons, for example. Although it sounds really bad to lose a qubit, the fact that you <em>know</em> when erasures happen actually...Thu, 28 Nov 2019 10:10:10 -0800
http://algassert.com/post/1907
http://algassert.com/post/1907Producing an N+1 Qubit CCZ State with an N Qubit Adder<p>Back in April, I read the pre-print <a href="https://arxiv.org/abs/1904.01124">"Lower bounds on the non-Clifford resources for quantum computations" by Beverland, Campbell, Howard, and Kliuchnikov</a>. It defines an amazingly simple metric, the "stabilizer nullity" of a state, which is the number of qubits in the state minus the number of Pauli product...Sun, 20 Oct 2019 11:10:10 -0700
http://algassert.com/post/1906
http://algassert.com/post/1906[Paper] Surface code dislocations have code distance L+O(1)Mon, 30 Sep 2019 05:10:10 -0700
http://algassert.com/2019/09/30/paper-dislocation-distance.html
http://algassert.com/2019/09/30/paper-dislocation-distance.htmlSpooky Pebble Games and Irreversible Uncomputation<p>In this post: extending pebble games to include measurement based uncomputation.</p> <p>A <a href="https://en.wikipedia.org/wiki/Pebble_game">pebble game</a> is a simplified abstraction of a reversible computation. A pebble game is played on a directed acyclic graph. Every node of the graph represents some intermediate value that can be computed and uncomputed. At any...Sun, 25 Aug 2019 11:10:10 -0700
http://algassert.com/post/1905
http://algassert.com/post/1905