2018/12/13 by Charles Stahl, Vedika Khemani, Stahl, Charles +3 · 1 citation
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Quantum Computing Algorithms and Architecture #Quantum Physics (quant-ph) #Quantum and electron transport phenomena #Quantum many-body systems #Statistical Mechanics (cond-mat.stat-mech) #cond-mat.stat-mech #quant-ph
paper · pdf · doi:10.48550/arxiv.1812.05589
arxiv created 2018/12/13 · openalex publication_date 2018/12/13 · arxiv updated 2018/12/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The butterfly velocity vB has been proposed as a characteristic velocity for information propagation in local systems. It can be measured by the ballistic spreading of local operators in time (or, equivalently, by out-of-time-ordered commutators). In general, this velocity can depend on the direction of spreading and, indeed, the asymmetry between different directions can be made arbitrarily large using arbitrarily deep quantum circuits. Nevertheless, in almost all examples of local time-independent Hamiltonians that have been examined thus far, this velocity is independent of the direction of information propagation. In this work, we present two models with asymmetric vB. The first is a time-independent Hamiltonian in one dimension with local, 3-site interactions. The second is a class of local unitary circuits, which we call n-staircases, where n serves as a tunable parameter interpolating from n=1 with symmetric spreading to n=∞ with completely chiral information propagation.