D-Wave Systems has commercially sold 2000 qubit quantum annealing systems.
D-Wave System announced reverse annealing. Reverse annealing lets programmers start the search for the best solution at a localized spot in solution space. The system will then focus on the area which may be more promising for the best answer.D-Wave enables users to have more control of qubits during the annealing process.
Reverse annealing allows users to start systematic searches for the best answer based upon their understanding of the solution space. It circumvents limitations on the number of qubits or the entanglement time by starting new searches in different locations.
D-Wave is working on a 5000 qubit system now and will likely install it with a customer in less than 2 years. They are also working to broaden connectivity on their chips.
IBM Quantum Experience in the cloud: 20 qubits at the end 2017 and a 50-qubit device has been built.
Rigetti Computing has a 19 qubit chip. Rigetti should have a 50 or 60 qubit system in 2018.
Google 22-qubit device (superconducting circuit), 49 qubits expected in 2018.
Harvard 51-qubit quantum simulator (Rydberg atoms in optical tweezers).
Dynamical phase transition in Ising-like systems; puzzles in defect (domain wall) density.
UMd 53-qubit quantum simulator (trapped ions). Dynamical phase transition in Ising-like systems; high-efficiency single-shot readout of many-body correlators.
ionQ: 32-qubit processor planned (trapped ions), with all-to-all connectivity.
Microsoft: is 2018 the year of the Majorana qubit?
There are other important metrics besides the number of qubits; in particular, the two-qubit gate error rate (currently over 1 per 1000) determines how large a quantum circuit can be executed with reasonable signal-to-noise.