Hardware wise, how does D-Wave achieve quantum annealing?

Question

Quantum computers have shown a new way to compute old problems. D-Wave has a quantum annealer, and Wikipedia describes the D-Wave quantum computer and its use of quantum annealing properties. Hardware wise, how does D-Wave achieve quantum annealing?

There may be many ways to achieve quantum annealing. D-Wave, being first on the market with quantum annealing hardware, therefore is open to more scrutiny (is their hardware open to such scrutiny?) Does D-Wave use a specific type of annealing at the atomic level (there could be one of many ways to achieve quantum annealing), or (in other words) are there many ways to achieve quantum annealing?

Answer 1

Quantum annealing as defined by Chakrabarti 1981 and later implemented by Kadowaki and Nishimori 1998 uses a varying transverse magnetic field to facilitate tunneling through the energy landscape of an optimization problem.

The system is prepared in the ground state of a Hamiltonian and then the transverse field is applied and slowly reduced (adiabatically) while the problem Hamiltonian is simultaneously 'turned on'. If this is done correctly, the system will remain in the ground state throughout the process and you'll have turned off the initial Hamiltonian and turned on the problem Hamiltonian with the system in the ground state (solution).

The temperature of the machine does not change (which is a common misconception), only the transverse magnetic field does.