Quantum state tomography is vital in quantum technology, aiming to reconstruct quantum states from experimental measurements. A novel method, classical shadow tomography (CST), significantly reduces the need for quantum measurements. CST's key aspect is to randomly rotate the quantum system using a unitary sampled from an ensemble. The shadow norm, or sample complexity, largely depends on the unitary ensemble. In this talk, we introduce a new protocol with a unitary ensemble called "contractive unitary," capable of contracting the Pauli operator size with high probability. This protocol achieves a sample complexity ~〖1.8〗^( k)  for predicting size-k Pauli operators' expectation when their precise location is known, much lower than the random Clifford ensemble's sample complexity. Even without the operators' location knowledge, our protocol still outperforms. Additionally, this contractive unitary aligns perfectly with the atom array quantum computation platform, enabling easy implementation in the atom array quantum processor.