  The partial transpose by which a subsystem's quantum state is solely
transposed is of unique importance in quantum information processing from both
fundamental and practical point of view. In this work, we present a practical
scheme to realize a physical approximation to the partial transpose using local
measurements on individual quantum systems and classical communication. We then
report its linear optical realization and show that the scheme works with no
dependence on local basis of given quantum states. A proof-of-principle
demonstration of entanglement detection using the physical approximation of the
partial transpose is also reported.
