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PennyLane: Automatic differentiation of hybrid quantum-classical computations
TLDR
PennyLane's core feature is the ability to compute gradients of variational quantum circuits in a way that is compatible with classical techniques such as backpropagation, and it extends the automatic differentiation algorithms common in optimization and machine learning to include quantum and hybrid computations.
Evaluating analytic gradients on quantum hardware
TLDR
This paper shows how gradients of expectation values of quantum measurements can be estimated using the same, or almost the same the architecture that executes the original circuit, and proposes recipes for the computation of gradients for continuous-variable circuits.
Quantum many-body systems out of equilibrium
How do closed quantum many-body systems driven out of equilibrium eventually achieve equilibration? And how do these systems thermalize, given that they comprise so many degrees of freedom? Progress
Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems.
TLDR
This work reviews selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics and elucidate the role played by key concepts, such as Lieb-Robinson bounds, entanglement growth, typicality arguments, quantum maximum entropy principles and the generalised Gibbs ensembles.
Locality of temperature
This work is concerned with thermal quantum states of Hamiltonians on spin and fermionic lattice systems with short range interactions. We provide results leading to a local definition of
Avoiding local minima in variational quantum eigensolvers with the natural gradient optimizer
TLDR
The results suggest that great care needs to be taken in the choice of gradient based optimizers and the parametrization for VQEs, with BFGS and ADAM failing more often and more severely than NatGrad.
Boson-Sampling in the light of sample complexity
TLDR
This work shows that in this setup, with probability exponentially close to one in the number of bosons, no symmetric algorithm can distinguish the Boson-Sampling distribution from the uniform one from fewer than exponentially many samples, which means that the two distributions are operationally indisti nguishable without detailed a priori knowledge.
Limits on nonlocal correlations from the structure of the local state space
The outcomes of measurements on entangled quantum systems can be nonlocally correlated. However, while it is easy to write down toy theories allowing arbitrary nonlocal correlations, those allowed in
Reliable quantum certification of photonic state preparations
TLDR
An experimentally friendly and reliable certification tool for photonic quantum technologies: an efficient certification test for experimental preparations of multimode pure Gaussian states, pure non-Gaussian states generated by linear-optical circuits with Fock-basis states of constant boson number as inputs.
Thermalization in nature and on a quantum computer.
TLDR
A novel perturbation theorem for physically relevant weak system-bath couplings that is applicable even in the thermodynamic limit is introduced and a fully general quantum algorithm for preparing Gibbs states on a quantum computer with a certified runtime and error bound is presented.
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