text: 339,91,1392951171636154376,1068545181576773632,Kenneth Brown,"Our new paper ""Optimizing Stabilizer Parities for Improved Logical Qubit Memories"" was posted to the arXiv yesterday <LINK> . Joint work with Chris Monroe's group @JQInews @DukeEngineering #DukeQuantumCenter My latest PhD graduate @DriptoDebroy (now @GoogleQuantumAI ) and I have been thinking about coherent rotation errors on quantum error codes for the past year and a bit. We noticed that for Shor codes you could reduce this error on one axis by changing the sign of the stabilizers. For even-distance Shor codes you can make the error vanish. This is an example of a broader set of codes developed by our colleagues, Jingzhen Hu, Qingzhong Liang, @nrenga92, and Robert Calderbank <LINK> #DukeQuantumCenter These codes are an example of weak collective decoherence free subspaces <LINK>, but are not concatenations of DFS with stabilizer codes like <LINK>. The DFS is part of the code. Our codes are not decoherence free subspaces just decoherence reducing. From a physics standpoint, we replace the very phase sensitive GHZ states (|000&gt;+|111&gt;) with the less phase sensitive states (|010&gt;+|101&gt;). Our experimental collaborators (Laird Egan, @crystalMIT13 , Andrew Risinger, Daiwei Zhu , Debopriyo Biswas, Marko Cetina, and Chris Monroe), tested it on 9-qubit states and saw a 4-fold increase in the logical T_2. For the weight-2 Z checks, changing the stabilizer sign is equivalent to switching from stabilizing ferromagnetic states to stabilizing antiferromagnetic states. In the appendix, we show numerically that switching the signs for weight-6 Z checks on the dual Shor code also helps. More broadly, for any stabilizer code, there are n-k subspaces that could be the code space. For independent random Pauli errors, it doesn't matter which subspace you use for your code. For correlated noise, it can make a huge difference. @cgranade @nrenga92 Yes. Exactly. I think what's cool about Jingzhen's et al. construction is that they arrived at it from a totally different direction and the DFS is just part of the code. edit: should be 2^(n-k) subspaces, where n is the number of data qubits and k is the number of logical qubits.",http://arxiv.org/abs/2105.05068,"We study variants of Shor's code that are adept at handling single-axis correlated idling errors, which are commonly observed in many quantum systems. By using the repetition code structure of the Shor's code basis states, we calculate the logical channel applied to the encoded information when subjected to coherent and correlated single qubit idling errors, followed by stabilizer measurement. Changing the signs of the stabilizer generators allows us to change how the coherent errors interfere, leading to a quantum error correcting code which performs as well as a classical repetition code of equivalent distance against these errors. We demonstrate a factor of 4 improvement of the logical memory in a distance-3 logical qubit implemented on a trapped-ion quantum computer. Even-distance versions of our Shor code variants are decoherence-free subspaces and fully robust to identical and independent coherent idling noise. ",Optimizing Stabilizer Parities for Improved Logical Qubit Memories,10,"['Our new paper ""Optimizing Stabilizer Parities for Improved Logical Qubit Memories"" was posted to the arXiv yesterday \n<LINK> . Joint work with Chris Monroe\'s group @JQInews @DukeEngineering #DukeQuantumCenter', 'My latest PhD graduate @DriptoDebroy (now @GoogleQuantumAI ) and I have been thinking about coherent rotation errors on quantum error codes for the past year and a bit. We noticed that for Shor codes you could reduce this error on one axis by changing the sign of the stabilizers.', 'For even-distance Shor codes you can make the error vanish.  This is an example of a broader set of codes developed by our colleagues, Jingzhen Hu, Qingzhong Liang, @nrenga92, and Robert Calderbank https://t.co/Z0hYvVWQmq #DukeQuantumCenter', 'These codes are an example of weak collective decoherence free subspaces https://t.co/VHDc6r1dui, but are not concatenations of DFS with stabilizer codes like https://t.co/SppPLCHQUG. The DFS is part of the code.', 'Our codes are not decoherence free subspaces just decoherence reducing. From a physics standpoint, we replace the very phase sensitive GHZ states (|000&gt;+|111&gt;) with the less phase sensitive states (|010&gt;+|101&gt;).', 'Our experimental collaborators (Laird Egan, @crystalMIT13 , Andrew Risinger, Daiwei Zhu , Debopriyo Biswas, Marko Cetina, and Chris Monroe), tested it on 9-qubit states and saw a 4-fold increase in the logical T_2.', 'For the weight-2 Z checks, changing the stabilizer sign is equivalent to switching from stabilizing ferromagnetic states to stabilizing antiferromagnetic states. In the appendix, we show numerically that switching the signs for weight-6 Z checks on the dual Shor code also helps.', ""More broadly, for any stabilizer code, there are n-k subspaces that could be the code space. For independent random Pauli errors, it doesn't matter which subspace you use for your code. For correlated noise, it can make a huge difference."", ""@cgranade @nrenga92 Yes. Exactly. I think what's cool about Jingzhen's et al. construction is that they arrived at it from a totally different direction and the DFS is just part of the code."", 'edit: should be 2^(n-k) subspaces, where n is the number of data qubits and k is the number of logical qubits.']",21,05,2150