Scope

Quantum computers are rapidly becoming more powerful and increasingly applicable to solve problems in the real world. They have the potential to solve extremely hard computational problems, which are currently intractable by conventional computers. Quantum optimization is an emerging field that focuses on using quantum computing technologies to solve hard optimization problems.

There are two main types of quantum computers, quantum annealers and quantum gate computers.

Quantum annealers are specially tailored to solve combinatorial optimization problems: they have a simpler architecture, and are more easily manufactured and are currently able to tackle larger problems as they have a larger number of qubits. These computers find (near) optimum solutions of a combinatorial optimization problem via quantum annealing, which is similar to traditional simulated annealing. Whereas simulated annealing uses ‘thermal’ fluctuations for convergence to the state of minimum energy (optimal solution), in quantum annealing the addition of quantum tunnelling provides a faster mechanism for moving between states and faster processing.

Quantum gate computers are general purpose quantum computers. These use quantum logic gates, a basic quantum circuit operating on a small number of qubits, for computation. Constructing an algorithm involves a fixed sequence of quantum logic gates. Some quantum algorithms, e.g., Grover's algorithm, have provable quantum speed-up. Among other things, these computers can be used to solve combinatorial optimization problems using the quantum approximate optimization algorithm.

Quantum computers have also given rise to quantum-inspired computers and quantum-inspired optimisation algorithms.

Quantum-inspired computers use dedicated conventional hardware technology to emulate/simulate quantum computers. These computers offer a similar programming interface of quantum computers and can currently solve much larger combinatorial optimization problems when compared to quantum computers and much faster than traditional computers.

Quantum-inspired optimisation algorithms use classical computers to simulate some physical phenomena such as superposition and entanglement to perform quantum computations, in an attempt to retain some of its benefit in conventional hardware when searching for solutions.

To solve optimization problems on a quantum annealer or on a quantum gate computer using the quantum approximate optimization algorithm, we need to reformulate them in a format suitable for the quantum hardware, in terms of qubits, biases and couplings between qubits. In mathematical terms, this requirement translates to reformulating the optimization problem as a pseudo-Boolean polynomial, and, in particular, as a Quadratic Unconstrained Binary Optimisation (QUBO) problem in the case of quantum annealers. This is closely related to the renowned Ising model. It constitutes a universal class, since in principle all combinatorial optimization problems can be formulated as QUBOs. In practice, some classes of optimization problems can be naturally mapped to a QUBO, whereas others are much more challenging to map. In quantum gates computers, Grover’s algorithm can be used to optimize a function by transforming the optimization problem into a series of decision problems. The most challenging part in this case is to select an appropriate representation of the problem to obtain the quadratic speedup of Grover’s algorithm compared to the classical computing algorithms for the same problem.

Content

A major application domain of quantum computers is solving hard combinatorial optimization problems. This is the emerging field of quantum optimization. The aim of the workshop is to provide a forum for both scientific presentations and discussion of issues related to quantum optimization.

As the algorithms quantum that computers use for optimization can be regarded as general types of heuristic optimization algorithms, there are potentially great benefits and synergy to bringing together the communities of quantum computing and heuristic optimization for mutual learning.

The workshop aims to be as inclusive as possible, and welcomes contributions from all areas broadly related to quantum optimization, and by researchers from both academia and industry.

Particular topics of interest include, but are not limited to:

Formulation of optimisation problems as QUBOs (including handling of non-binary representations and constraints)
Fitness landscape analysis of QUBOs
Novel search algorithms to solve QUBOs
Experimental comparisons on QUBO benchmarks
Theoretical analysis of search algorithms for QUBOs
Speed-up experiments on traditional hardware vs quantum(-inspired) hardware
Decomposition of optimisation problems for quantum hardware
Application of the quantum approximate optimization algorithm
Application of Grover's algorithm to solve optimisation problems
Novel quantum-inspired optimisation algorithms
Optimization/discovery of quantum circuits
Quantum optimisation for machine learning problems
Optical Annealing
Dealing with noise in quantum computing
Quantum Gates’ optimisation
Quantum Coherent Control