Abstract: The present disclosure provides embodiments for optical cavity apparatuses and methods for assembling such apparatuses. For example, an optical cavity apparatus includes a body and two mirrors that are attached to the body and form an optical cavity having an optical path inside the body. Furthermore, the body has an opening that allows gas to be pumped out of the optical cavity; and includes a closing means attached to the opening that can be closed for maintaining, after pumping the gas out of the optical path, a negative pressure in the optical cavity.

Abstract: The present disclosure provides entangling two or more trapped ions wherein a common motional mode of the ions is used by conditionally, depending on an internal state of the ions, exciting and/or de-exciting the common motional mode. The common motional mode is conditionally excited/de-excited by inducing, on each of the two or more trapped ions respective perpendicular state-dependent forces (SDFs) that are modulated in accordance with the frequency of the motional mode. Each of the perpendicular SDFs can be induced by a laser beam and acts perpendicular to the propagation direction of the laser beam that induces it. The SDFs may be modulated by modulating an intensity and/or an amplitude of the electromagnetic field of the first laser beam, changing a position and/or a direction of the first laser beam relative to the first trapped ion, and/or including light of different frequencies into the laser beam.

Abstract: Some embodiments in the present disclosure relate to an apparatus and methods to excite a trapped ion. A first laser beam and a second laser beam pass through at least one common lens of an objective. The two laser beams are focused by said objective at the position of the trapped ion. A moving standing wave is generated at the position of the trapped ion, which induces a force on the trapped ion. Two ions may be entangled by generating such moving standing wave at the respective positions of both of said ions.