Title: Asymptotically good CSS codes in which physical transversal T realizes logical transversal S^{\dag} Speaker:  Navin Kashyap (IISC, Bangalore) Date & Time:  November 25, 2025, 11:00am Where to Attend:  ATL 3100A and Virtual Via Zoom: https://umd.zoom.us/j/9137887602?pwd=ei84WW1MZG9aUWtiempMWVNCWVY3dz09&omn=98012977889 Meeting ID: 913 788 7602 Passcode: 542956
CSS-T codes are quantum stabilizer codes constructed using the Calderbank-Shor-Steane (CSS) framework that admit the physical transversal T-gate as a logical operator. Ideally, we want the physical transversal T to realize the logical transversal T (or some other logical non-Clifford gate), but it seems difficult to construct CSS-T codes with good [[n,k,d]] parameters having this property. Some recent progress on this was made by Berardini et al. (2025), who constructed asymptotically good families of [[n,k,d]] CSS-T codes, where "asymptotically good" means that both k and d grow linearly with n. However, in these codes, the transversal T-gate realizes only the logical identity operator. In this talk, we show how a construction due to Jain and Albert (2024) can be extended to obtain an asymptotically good family of CSS-T codes in which the physical transversal T-gate implements the logical transversal S^{\dag}-gate. Along the way, we plug a gap in a characterization by Rengaswamy et al. (2020) of CSS-T codes in which the physical transversal T is the logical identity, and also in another characterization of when physical transversal T realizes the logical transversal T. We further resolve an open problem on CSS-T codes posed by Jain and Albert.
The talk is based on joint work with K. Sai Mineesh Reddy.
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