Circuit-QED simulator of the Bose-Hubbard model for quantum spin dynamics

  1. Ivan V. Dudinets,
  2. Jaehee Kim,
  3. Tomás Ramos,
  4. Aleksey K. Fedorov,
  5. Vladimir I Man'ko,
  6. and Joonsuk Huh
We demonstrate an experimentally feasible circuit-QED Bose-Hubbard simulator that reproduces the complex spin dynamics of Heisenberg models. Our method relies on mapping spin-1/2 systems
onto bosonic states via the polynomially expanded Holstein-Primakoff (HP) transformation. The HP transformation translates the intricate behavior of spins into a representation that is compatible with bosonic devices like those in a circuit QED setup. For comparison, we also implement the Dyson-Maleev (DM) encoding for spin-1/2 and show that, in this limit, DM and HP are equivalent. We show the equivalence of the DM and the HP transformations for spin-1/2 systems. Rigorous numerical analyses confirm the effectiveness of our HP-based protocol. Specifically, we obtain the concurrence between the spin dynamics and the behavior of microwave photons within our circuit QED-based analog simulator that is designed for the Bose-Hubbard model. By utilizing the microwave photons inherent to circuit QED devices, our framework presents an accessible, scalable avenue for probing quantum spin dynamics in an experimentally viable setting.

Quantum emulation of molecular force fields: A blueprint for a superconducting architecture

  1. Diego G. Olivares,
  2. Borja Peropadre,
  3. Joonsuk Huh,
  4. and Juan José García-Ripoll
In this work, we propose a flexible architecture of microwave resonators with tuneable couplings to perform quantum simulations of molecular chemistry problems. The architecture builds
on the experience of the D-Wave design, working with nearly harmonic circuits instead of with qubits. This architecture, or modifications of it, can be used to emulate molecular processes such as vibronic transitions. Furthermore, we discuss several aspects of these emulations, such as dynamical ranges of the physical parameters, quenching times necessary for diabaticity and finally the possibility of implementing anharmonic corrections to the force fields by exploiting certain nonlinear features of superconducting devices.

Dynamical Casimir Effect for Gaussian Boson Sampling

  1. Borja Peropadre,
  2. Joonsuk Huh,
  3. and Carlos Sabín
We show that the Dynamical Casimir Effect (DCE), realized on two multimode coplanar waveguide resonators, implements a gaussian boson sampler (GBS). The appropriate choice of the mirror
acceleration that couples both resonators translates into the desired initial gaussian state and many-boson interference in a boson sampling network. In particular, we show that the proposed quantum simulator naturally performs a classically hard task, known as scattershot boson sampling. Our result unveils an unprecedented computational power of DCE, and paves the way for using DCE as a resource for quantum simulation.

Microwave Boson Sampling

  1. Borja Peropadre,
  2. Gian Giacomo Guerreschi,
  3. Joonsuk Huh,
  4. and Alán Aspuru-Guzik
The first post-classical computation will most probably be performed not on a universal quantum computer, but rather on a dedicated quantum hardware. A strong candidate for achieving
this is represented by the task of sampling from the output distribution of linear quantum optical networks. This problem, known as boson sampling, has recently been shown to be intractable for any classical computer, but it is naturally carried out by running the corresponding experiment. However, only small scale realizations of boson sampling experiments have been demonstrated to date. Their main limitation is related to the non-deterministic state preparation and inefficient measurement step. Here, we propose an alternative setup to implement boson sampling that is based on microwave photons and not on optical photons. The certified scalability of superconducting devices indicates that this direction is promising for a large-scale implementation of boson sampling and allows for more flexible features like arbitrary state preparation and efficient photon-number measurements.

Towards Outperforming Classical Algorithms with Analog Quantum Simulators

  1. Sarah Mostame,
  2. Joonsuk Huh,
  3. Christoph Kreisbeck,
  4. Andrew J. Kerman,
  5. Takatoshi Fujita,
  6. Alexander Eisfeld,
  7. and Alán Aspuru-Guzik
With quantum computers being out of reach for now, quantum simulators are the alternative devices for efficient and more exact simulation of problems that are challenging on conventional
computers. Quantum simulators are classified into analog and digital, with the possibility of constructing „hybrid“ simulators by combining both techniques. In this paper, we focus on analog quantum simulators of open quantum systems and address the limit that they can beat classical computers. In particular, as an example, we discuss simulation of the chlorosome light-harvesting antenna from green sulfur bacteria with over 250 phonon modes coupled to each electronic state. Furthermore, we propose physical setups that can be used to reproduce the quantum dynamics of a standard and multiple-mode Holstein model. The proposed scheme is based on currently available technology of superconducting circuits consist of flux qubits and quantum oscillators.