Simulation of collective neutrino oscillations on a quantum computer

Abstract

In astrophysical scenarios with large neutrino density, like supernovae and the early universe, the presence of neutrino-neutrino interactions can give rise to collective flavor oscillations in the out-ofequilibrium collective dynamics of a neutrino cloud. The role of quantum correlations in these phenomena is not yet well understood, in large part due to complications in solving for the real-time evolution of the strongly coupled many-body system. Future fault-tolerant quantum computers hold the promise to overcome much of these limitations and provide direct access to the correlated neutrino dynamic. In this work, we present the first simulation of a small system of interacting neutrinos using current generation quantum devices. We introduce a strategy to overcome limitations in the natural connectivity of the qubits and use it to track the evolution of entanglement in real-time. The results show the critical importance of error-mitigation techniques to extract meaningful results for entanglement measures using noisy, near term, quantum devices.

Variational approaches to constructing the many-body nuclear ground state for quantum computing

“…[37]. We notice that given the fact that we are using very shallow circuits (with a maximum number of 3 CNOT gates 4) we did not use other methods such as exponential extrapolation, a method that was showed to lead to a significant improvement for observables calculated using significantly higher gate depths [38] than the present ones . The error mitigated results are more in agreement with the numerically exact ones, although not in complete agreement.…”

Nuclear two point correlation functions on a quantum-computer

“…[23] (see also Refs. [24,[42][43][44] and the appendices of [25,45] for more details on our implementation).…”

Hybridized Methods for Quantum Simulation in the Interaction Picture

“…[47,48] for reviews). Due to the presence of interactions, many-body effects and quantum correlations could be important in understanding these phenomena and a number of studies is underway with a variety of techniques: from exact diagonalization [49] to Bethe-ansatz solutions [50], from tensor networks [51,52] to digital quantum simulations [53,54]. Quantum computing might offer a promising route to study these phenomena in situations where the entanglement entropy grows too fast with system size for tensor network simulations to remain feasible.…”

“…Interestingly, using the swap-network protocol from Ref. [53] (and inspired from their fermionic variant [56]), this cost is not affected by limited connectivity in the device despite the interaction being all-to-all. This cost also coincides with the optimal scaling with λ permitted by the no-fast forwarding theorem [57], despite being a loworder formula that has inferior scaling with respect to the other parameters relative to alternative simulation methods.…”