Contractive Schrodinger cat states for afree mass

Contractive states for a free quantum particle were introduced by Yuen (Yuen H P 1983 Phys. Rev. Lett. 51 719) in an attempt to evade the standard quantum limit for repeated position measurements. We show how appropriate families of two- and three-component 'Schrodinger cat states' are able to support non-trivial correlations between the position and momentum observables leading to contractive behaviour. The existence of contractive Schrodinger cat states is suggestive of potential novel roles of non-classical states for precision measurement schemes.