Speaker
Description
We introduce a novel breakthrough approach to evaluate the nonstabilizerness of an N-qubits Matrix Product State (MPS) with bond dimension $\chi$. In particular, we consider the recently introduced Stabilizer Rényi Entropies (SREs). We show that the exponentially hard evaluation of the SREs can be achieved by means of a simple perfect sampling of the many-body wave function over the Pauli string configurations. The MPS representation enables such a sampling in an efficient way with a computational cost O(N$\chi^3$), no matter the Rényi index $n>0$. The accuracy, being size-independent, can be arbitrarily improved with the number of samples. We benchmark our method over randomly generated magic states, as well as in the ground-state of the quantum Ising chain. Exploiting the extremely favourable scaling, we easily have access to the non-equilibrium dynamics of the SREs after a quantum quench.
| Abstract category | Numerical Methods |
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