Method and apparatus for quantum information processing using entangled neutral-atom qubits
A method for preparing an entangled quantum state of an atomic ensemble is provided. The method includes loading each atom of the atomic ensemble into a respective optical trap; placing each atom of the atomic ensemble into a same first atomic quantum state by impingement of pump radiation; approaching the atoms of the atomic ensemble to within a dipole-dipole interaction length of each other; Rydberg-dressing the atomic ensemble; during the Rydberg-dressing operation, exciting the atomic ensemble with a Raman pulse tuned to stimulate a ground-state hyperfine transition from the first atomic quantum state to a second atomic quantum state; and separating the atoms of the atomic ensemble by more than a dipole-dipole interaction length.
1. A method for preparing an entangled quantum state of an atomic ensemble that consists of two or more identical atoms, comprising:
loading each atom of the atomic ensemble into a respective optical trap;
placing each atom of the atomic ensemble into a same first atomic quantum state by impingement of pump radiation;
approaching the atoms of the atomic ensemble to within a dipole-dipole interaction length of each other;
in a Rydberg-dressing operation, impinging a Rydberg-dressing laser beam on the atomic ensemble;
during the Rydberg-dressing operation, exciting the atomic ensemble with a Raman pulse; and
separating the atoms of the atomic ensemble by more than a dipole-dipole interaction length;
wherein:
the Rydberg-dressing operation has a specified transition from an atomic ground state to a target Rydberg-atom principal quantum number, and the Rydberg-dressing laser beam only partially stimulates the specified transition; and
the Raman pulse is tuned to stimulate a ground-state hyperfine transition from the first atomic quantum state to a second atomic quantum state.
2. The method of claim 1 , wherein the Rydberg-dressing laser beam is detuned so as to only partially stimulate the specified transition.
3. The method of claim 1 , wherein the Rydberg-dressing laser beam is adiabatically ramped so as to only partially stimulate the specified transition.
4. The method of claim 1 , wherein: the optical trap for each respective atom of the atomic ensemble is provided by a trapping laser beam deflected by a modulator.
5. The method of claim 4 , wherein the modulator is an acousto-optic modulator (AOM), the AOM is driven by a respective, independently controllable drive signal for each of the optical traps; and the approaching and separating steps are performed by sweeping the respective AOM drive signals.
6. The method of claim 4 , wherein the modulator is a spatial light modulator.
7. The method of claim 1 , wherein the atomic ensemble consists of cesium-133 atoms.
8. The method of claim 1 , wherein the target Rydberg-atom principal quantum number is at least 20.
9. The method of claim 1 , wherein the target Rydberg-atom principal quantum number is 64.
10. The method of claim 1 , wherein the atomic ensemble consists of two atoms.