JPA does not define such a capability. But you can do it using Hibernate calls:
final org.hibernate.engine.spi.SessionImplementor session = em.unwrap( org.hibernate.engine.spi.SessionImplementor.class );
final org.hibernate.engine.spi.PersistenceContext pc = session.getPersistenceContext();
final Map.Entry<Object,org.hibernate.engine.spi.EntityEntry>[] entityEntries = pc.reentrantSafeEntityEntries();
entityEntries
here is an array of Map.Entry instances whose "key" is the entity itself and whose value is an instance of org.hibernate.engine.spi.EntityEntry
that describes various info about the entity, including information like EntityEntry.getStatus().