7 papers
Online Shadow Tomography Matching the Classical Bounds
Sitan Chen, Ryan O'Donnell, Angelos Pelecanos +1
In Online Shadow Tomography, we are given copies of an unknown -dimensional quantum state , an adversary (adaptively) proposes a sequence of bounded observables $A^{(1)},\ldo…
The Keyl-Werner algorithm is not optimal for spectrum estimation
Angelos Pelecanos, Jack Spilecki, Ewin Tang +1
The paper presents a new algorithm that estimates the eigenvalues of a quantum state using fewer copies than the traditional Keyl‑Werner method, achieving constant error with O(d^2…
Improved Lower Bounds for QAC0
Malvika Raj Joshi, Avishay Tal, Francisca Vasconcelos +1
In this work, we prove the strongest known lower bounds for QAC, allowing polynomially many gates and ancillae. Our main results show that: (1) Depth-3 QAC circuits cannot…
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…
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 copies of an unknown rank- mixed state and asked to produce an estimator of . In…
Optimal lower bounds for quantum state tomography
Thilo Scharnhorst, Jack Spilecki, John Wright
We show that copies are necessary to learn a rank mixed state up to error in trace distance. This match…