## Francesco Tacchino

*University of Pavia*

Francesco Tacchino received his B.Sc. in Physics (2014) and his M.Sc. in Physical Sciences (2016) from the University of Pavia, Italy, and he is currently graduate student at the same university, where he works on quantum science and condensed matter physics.His research focuses on quantum optics, open quantum systems theory and phenomenology, quantum computing and quantum simulations, with particular attention to superconducting and hybrid platforms and to near-term applications. He is interested in expanding the connections between fundamental physics and technology, by developing models of cavity and circuit QED devices and investigating the quantum thermodynamics of driven-dissipative systems.

Digital quantum simulators are among the most appealing applications of a quantum computer [1]. In principle, any model that can be mapped onto a spin-type Hamiltonian can be encoded in a digital quantum simulator. Then, its time evolution can be solved exactly, thus overcoming the unavoidable exponential scaling of computational resources that is inherent to quantum manybody physics.

Here I will review our recent theoretical proposal for a universal, scalable, and integrated quantum computing platform based on tunable nonlinear electromechanical nano-oscillators. I will describe a minimal architecture where qubits could be encoded in the anharmonic vibrational modes of nanomechanical resonators coupled to a superconducting nanocircuitry [2]. Practical realizations of such qubits can be envisioned as suspended nanotubes, two-dimensional nanomembranes (e.g. graphene sheets), or cantilevers. An effective scheme to induce large single-phonon nonlinearities in nano-electromechanical devices will also be explicitly discussed. In the proposed platform, single-qubit rotations can be implemented by using external static and modulated electric fields acting locally on a single nanoresonator, while two-qubits gates would be efficiently realized by mediating their effective coupling through virtual fluctuations of an intermediate superconducting artificial atom, such as a transmon. At difference with the use of the latter superconducting elements as qubits, their coherence time (T_{2}) is essentially irrelevant here, a fact that helps envisioning considerable prospects for scalability.

As explicit proof-of-principle examples of the electromechanical quantum simulator, I will show, through the results of numerical simulations, the very high fidelities that can be reached for the digital quantum simulation of a few model Hamiltonians, such as the Ising model in a transverse field (TIM).

Finally, I will show how we challenged our proposed simulator with an existing one, the IBM-Q quantum computer freely available for cloud quantum computation [3]. Such a state-of-art implementation of an actual quantum computer, which employs purely superconducting qubits in a microwave nanocircuit, can also perform a digital quantum simulation of a few targeted models of interest in condensed matter physics. Nevertheless, encoding the qubits in mechanical degrees of freedom would allow to outperform the current implementations both in terms of fidelity as well as scalability of the quantum simulation.

[1] S. Lloyd, Science **273**, 1073 (1996)

[2] F. Tacchino *et al.*, Physical Review B **97**, 214302 (2018)

[3] https://www.research.ibm.com/ibm-q/

Quantum simulation , Superconducting circuits , Solid states and hybrid systems