Qu&Co comments on this publication:

Boson sampling is a rudimentary quantum algorithm tailored to the platform of photons in linear optics. Prior to this paper by Neville et al, it was believed that Boson-sampling was a good candidate to be the first to experimentally show quantum supremacy. However, Neville et al. show that this would require a technological step change, reaching photon numbers of over 50 and ultra-low loss interferometers with thousands of modes. It is therefore highly unlikely that Boson-sampling experiments will win the 'quantum supremacy race' currently believed to be led by semiconductor-qubit platforms.

Qu&Co comments on this publication:

One of the most popular techniques for error-correction is the surface code with logical 2-qubit operations realized via so-called lattice surgery. This popularity is explained a.o. by its high estimated error-correction threshold of 1% and relatively simple correction procedure. In this paper, De Beaudrap et al. demonstrate that lattice surgery is a model for the ZX calculus, an abstract graphical language for tensor networks. ZX calculus therefore provides a ready-made practical 'language' for discussing computations realized using surface codes via lattice surgery.

Qu&Co comments on this publication:

In this paper, Ambainis et al. study quantum algorithms on search trees of unknown structure, in a model where the tree can be discovered by local exploration. They construct a quantum algorithm which, given a search tree of depth at most n, estimates the size of the tree T with an upper-bound of sqrt(nT) steps. They apply their results to improve the time-complexity of a classical backtracking algorithm and to develop a quantum algorithm for evaluating AND-OR formulas in 2-player game type models.

Qu&Co comments on this publication:

Many quantum machine learning algorithms use a quantum linear system solver (QLS) as a subroutine. HHL type QLS algorithms achieve exponential speedup over classical algorithms for sparse matrices, however for dense matrices the speed-up is less profound, In this paper, Wossnig et al. describe a new QLS algorithm using the quantum singular value estimation. When applied to a dense matrix with spectral norm bounded by a constant, the runtime of this proposed algorithm is bounded by O(κ^2 √n.polylog(n)/e), which is a quadratic improvement over HHL based QLS algorithms. In comparison, classical (non-quantum) linear system solvers typically require time O(n^3) for dense matrices.

Qu&Co comments on this publication:

Quantum computers can be used to address molecular structure, materials science and condensed matter physics problems, which currently stretch the limits of existing high-performance computing resources. Finding exact numerical solutions to these interacting fermion problems has exponential cost, while Monte Carlo methods are plagued by the fermionic sign problem. In Quantum Computational Chemistry solutions, the Variational Quantum Eigensolver (VQE) algorithm offers a hybrid classical-quantum, and thus low quantum circuit depth, alternative to the Phase Estimation algorithm used to measure the ground-state energy of a molecular Hamiltonian. In VQE the quantum computer is used to prepare variational trial states that depend on a set of parameters. Then, the expectation value of the energy is estimated and used by a classical optimizer to generate a new set of improved parameters. The advantage of VQE over classical simulation methods is that in VQE one can prepare trial states that are not amenable to efficient classical numerics. In this paper, Kandala et al. demonstrate the experimental results for determining the ground state energy for molecules of increasing size, up to BeH2 using the VQE algorithm.

Qu&Co comments on this publication:

In this article Boixo et al. (Google/UCSB) present their proposed quantum supremacy experiment. Their proposal uses the task of sampling from the output distributions of (pseudo-) random quantum circuits, which, classically, requires a direct numerical simulation of the circuit, with computational cost exponential in the number of qubits.. They estimate that in such experiment, quantum supremacy can be achieved in the near-term with approximately 50 superconducting qubits. Furthermore they introduce cross entropy as a practical test of quantum supremacy.

Qu&Co comments on this publication:

Most near-term quantum-computational chemistry experiments have so-far been implemented by applying the Variational Quantum Eigensolver (VQE) classical-quantum hybrid algorithm as an alternative to Quantum Phase Estimation (QPE). This is due to the fact that QPE requires many orders of magnitude more quantum gates than is feasible with typical coherence times of current and near-term quantum-processors. As an alternative, in this paper, Paesani et al. report experimental results of a recently proposed adaptive Bayesian approach to quantum phase estimation and use it to simulate molecular energies on a Silicon quantum photonic device. The approach is verified to be well suited for NISQ quantum-processors by investigating its superior robustness to noise and decoherence compared to the iterative phase estimation algorithm. There results shows a promising route to unlock the power of QPE much sooner than previously believed possible.

Qu&Co comments on this publication:

This essay by The Economist journalist Jason Palmer provides an introductory overview of the state of development of different quantum-technologies, their potential use-cases and current investments and patent applications per country

Qu&Co comments on this publication:

Quantum sensing and metrology may benefit from a spatially distributed network architecture employing entangled states and measurements to enhance precision. Given the challenges faced in the creation and manipulation of entangled states, a complete understanding of when entanglement is (and is not) critical to optimizing estimation precision is importance. In this paper, Proctor et al. introduce a general model for a network of quantum sensors, and use this model to determine whether precision enhancement can be achieved in a range of practical applications.

Qu&Co comments on this publication:

Several physical platforms are aiming to realize a fully programmable, coherent and scalable quantum annealing device. In this paper, Glaetzle et al. show that combining a quantum simulation toolbox for Rydberg atoms with the Lechner-Hauke-Zoller (LHZ) architecture allows one to build a prototype for a coherent adiabatic quantum computer with all-to-all Ising interactions. 

Qu&Co comments on this publication:

Networks of coupled optical parametric oscillators (OPOs) are an alternative physical system for solving Ising type problems. Theoretical/numerical investigations have shown that in principle quantum effects (like entanglement between delay-coupled pulses) can play meaningful roles in such systems. In this paper, McMahon et al. (and an earlier paper of Inagaki et al.), show that this type of architecture is relatively scalable and can be used to solve max cut problems accurately, although in the current prototype devices the quantum features are 'washed out' by high round-trip losses (typically 10 dB), to the point that a purely semi-classical description of the system is sufficient to explain all the observed experimental results. The next step would be to realize this architecture in a system where the quantum nature is not lost.

Qu&Co comments on this publication:

In this paper, Venturelli et al. present a quantum annealing solver for the renowned job-shop scheduling problem (JSP). They formulate the problem as a time-indexed quadratic unconstrained binary optimization problem, several pre-processing and graph embedding strategies are employed to compile optimally parametrized families of the JSP for scheduling instances of up to six jobs and six machines on the D-Wave Systems Vesuvius (DW2) processor. Problem simplifications and partitioning algorithms are discussed and the results from the processor are compared against state-of-the-art global-optimum solvers.

Page 8 of 9

What's Interesting?

How can we help you?

Invalid Input

Invalid Input

Invalid Input

Invalid Input

Invalid Input

Invalid Input

Copyright © Qu & Co BV
close