Some aspects are directed to a method of operating an apparatus, the apparatus comprising a first quantum system having a plurality of coherent quantum states, the first quantum system being coupled to a second quantum system, the method comprising providing an input energy signal to the second quantum system that stimulates energy transfer between the first quantum system and the second quantum system and that causes net dissipation of energy to be output from the second quantum system, wherein the input energy signal includes at least two components having different frequencies and each having an amplitude and a phase, and adiabatically varying the amplitude and the phase of the at least two components of the input energy signal to cause a change in one or more of the plurality of coherent quantum states of the first quantum system.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method of operating an apparatus, the apparatus comprising a first quantum system having a plurality of coherent quantum states, the first quantum system being coupled to a second quantum system, the method comprising: providing an input energy signal to the second quantum system that stimulates energy transfer between the first quantum system and the second quantum system and that causes net dissipation of energy to be output from the second quantum system, wherein the input energy signal includes at least two components having different frequencies and each having an amplitude and a phase; and adiabatically varying the amplitude and the phase of the at least two components of the input energy signal to cause a change in one or more of the plurality of coherent quantum states of the first quantum system. 2. The method of claim 1, wherein the change in one or more of the plurality of coherent quantum states of the first quantum system is a phase change of a first coherent quantum state of the plurality of coherent quantum states relative to the other coherent quantum states of the plurality of coherent quantum states. 3. The method of claim 1, wherein the change in one or more of the plurality of coherent quantum states of the first quantum system is a population transfer between a second coherent quantum state of the plurality of coherent quantum states and a third coherent quantum state of the plurality of coherent quantum states. 4. The method of claim 1, wherein said adiabatic variation of the amplitude and the phase of the at least two components of the input energy signal is performed such that each of the amplitude and the phase of each of the at least two components of the input energy signal has the same initial and final value before and after the adiabatic variation. 5. The method of claim 1, wherein the first quantum system is coupled to the second quantum system via a non-linear element. 6. The method of claim 5, wherein the non-linear element is a Josephson junction. 7. The method of claim 1, wherein: the first quantum system is a first resonant cavity, the second quantum system is a second resonant cavity, the input energy signal is an input photon signal, and said energy transfer between the first quantum system and the second quantum system comprises photon conversion between the first quantum system and the second quantum system. 8. The method of claim 7, wherein a quality (Q) factor of the first resonant cavity is greater than a Q-factor of the second resonant cavity. 9. The method of claim 7, wherein a first component of the input photon signal has a first frequency and a second component of the input photon signal has a second frequency, and wherein a difference between the first frequency and the second frequency is equal to a resonant frequency of the first resonant cavity. 10. The method of claim 7, wherein a third component of the input photon signal has a third frequency equal to a resonant frequency of the second resonant cavity. 11. The method of claim 7, wherein the photon conversion between the first quantum system and the second quantum system comprises photon conversion from the first quantum system to the second quantum system and photon conversion from the second quantum system to the first quantum system 12. The method of claim 11, wherein the photon conversion from the first quantum system to the second quantum system comprises a superposition of: two photons of the first quantum system converting to one photon of the second quantum system; and one photon of the first quantum system converting to one photon of the second quantum system. 13. The method of claim 1, further comprising, prior to said providing the input energy, initializing the first quantum system in a superposition of at least two of the plurality of coherent states. 14. The method of claim 1, wherein the first quantum system has at least three coherent quantum states. 15. An apparatus comprising: a first quantum system having a plurality of coherent quantum states; a second quantum system coupled to the first quantum system; at least one energy source; and at least one controller configured to: providing an input energy signal from the at least one energy source to the second quantum system that stimulates energy transfer between the first quantum system and the second quantum system and that causes net dissipation of energy to be output from the second quantum system, wherein the input energy signal includes at least two components having different frequencies and each having an amplitude and a phase; and adiabatically vary the amplitude and the phase of the at least two components of the input energy signal to cause a change in one or more of the plurality of coherent quantum states of the first quantum system. 16. The apparatus of claim 15, wherein the first quantum system is coupled to the second quantum system a Josephson junction. 17. The apparatus of claim 15, wherein: the first quantum system is a first resonant cavity, the second quantum system is a second resonant cavity, the at least one energy source is an electromagnetic radiation source, the input energy signal is an input photon signal, and said energy transfer between the first quantum system and the second quantum system comprises photon conversion between the first quantum system and the second quantum system.