Efficient preparation and verification of quantum states


How can we efficiently prepare complex many-body states on near-term quantum devices, and how can we verify the success of such a preparation?

These are the questions investigated by a team of researchers from Munich and Leiden, together with our research group leader Norbert Schuch, in a new paper in the open access journal Physical Review Research.

In their work, they devise a large class of states which can be prepared efficiently by quantum simulators and computers, using so-called adiabatic evolution. The states form a broad subclass of tensor network states, which include a diverse range of states of practical interest. As a first key contribution of their work, they show that there exists a systematic hierarchy of efficiently solvable problems – semidefinite programs – which allows to lower bound the speed at which this preparation can be carried out reliably.

The second key contribution of the paper is to provide ways in which the successful preparation of the state can be tested or certified. On the one hand, this includes a hierarchy of measurements with known outcomes whose correctness allows to certify the accurate preparation of the target state. On the other hand, this also encompasses methods which can be applied in untrusted scenarios, where the task of preparation is handed over to a third party, or one does not fully trust the experimental device, and one needs to make sure that the third party is indeed in possession of an actual quantum device.

If you want to learn more, check out the paper at Physical Review Research (open access), or on the arXiv.

This work has received support through the ERC grant SEQUAM.