The detection loophole in Hardy's nonlocality theorem and minimum detection efficiency

Abstract

The detection loophole is discussed in connection with Hardy's nonlocality theorem. An inequality that must be satisfied in order that the Hardy nonlocality theorem avoids the detection loophole is derived. The minimum detector efficiency is calculated to be 2/3. It is shown that the minimum value obtainable theoretically using a version of Bell's inequalities is 2/3.