Jack Spilecki

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quant-ph2025

Mixed state tomography reduces to pure state tomography

Angelos Pelecanos, Jack Spilecki, Ewin Tang +1

A longstanding belief in quantum tomography is that estimating a mixed state is far harder than estimating a pure state. This is borne out in the mathematics, where mixed state alg…

quant-ph2025

The debiased Keyl's algorithm: a new unbiased estimator for full state tomography

Angelos Pelecanos, Jack Spilecki, John Wright

In the problem of quantum state tomography, one is given $n$ copies of an unknown rank- $r$ mixed state $ρ \in C^{d \times d}$ and asked to produce an estimator of $ρ$ . In t…

quant-ph2025

Optimal lower bounds for quantum state tomography

Thilo Scharnhorst, Jack Spilecki, John Wright

We show that $n = Ω (r d / ε^{2})$ copies are necessary to learn a rank $r$ mixed state $ρ \in C^{d \times d}$ up to error $ε$ in trace distance. This matches…