European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Fondazione Bruno Kessler); Villa Tambosi, Strada delle Tabarelle 286, I-38123 Villazzano (TN), Italy
G. Garberoglio
European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Fondazione Bruno Kessler); Villa Tambosi, Strada delle Tabarelle 286, I-38123 Villazzano (TN), Italy
D. Maragnano
Dipartimento di Fisica, Università di Pavia, Via Bassi 6, 27100 Pavia, Italy
M. Dapor
European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*, Fondazione Bruno Kessler); Villa Tambosi, Strada delle Tabarelle 286, I-38123 Villazzano (TN), Italy
M. Liscidini
Dipartimento di Fisica, Università di Pavia, Via Bassi 6, 27100 Pavia, Italy
Quantum state tomography (QST) aims at reconstructing the state of a quantum system. However, in conventional QST, the number of measurements scales exponentially with the number of qubits. Here, we propose a QST protocol, in which the introduction of a threshold allows one to drastically reduce the number of measurements required for the reconstruction of the state density matrix without compromising the result accuracy. In addition, one can also use the same approach to reconstruct an approximated density matrix tailoring the number of measurements on the available resources. We experimentally demonstrate this protocol by performing the tomography of states up to 7 qubits. We show that our approach can lead to results in agreement with those obtained by QST even when the number of measurements is reduced by more than two orders of magnitude.