Quantum state engineering in the presence of noise

TKM Institutsseminar

Vortragender:

Edward Medina-Guerra

Datum:

19.05.2022 12:30

Ort:

Room 10.01, Bldg. 30.23, Campus South and via Zoom

Zugehörigkeit:

Weizmann Institute

Gastgeber:

Igor Gornyi

Abstract

The quantum state of a subsystem belonging to a bipartite system can be modified by performing local measurements on its complementary party. This type of correlation is called quantum steering and is one of the pillars of quantum state engineering. In this work, we study the robustness against errors of a particular quantum steering protocol presented by Roy et al. in [S.Roy, J. T. Chalker, I. V. Gornyi, and Y. Gefen. Physical Review Research, 2 (3), 033347, 2020]. The protocol consists of steering an arbitrary initial state of a quantum system towards a predetermined pure target state by the consecutive iteration of the following three steps: first, a product state is formed with the state of the steered system and the state of m independently prepared ancillary systems (also called “detectors”); second, the product state evolves during a finite time under the action of a tailor-made detector-system Hamiltonian that induces correlations between the detector and system; and third, a partial trace is taken over the detectors to get the updated state of the system (this is referred to as a “blind measurement”). For this protocol, we consider two types of errors of probabilistic nature: static and dynamic, where the probability of the latter changes after each steering step. We show that the protocol is not particularly robust against the static error consisting of wrongly prepared ancillary states. As for dynamical errors, such as environmentally induced stochastic noise, the protocol shows robustness only under a particular set of conditions. The steering of a qubit towards an arbitrary point on the Bloch sphere is given as an example.