Patent ID: 8315969

Claim:
A method of estimating a quantum state of a quantum mechanical system, the method comprising: applying a plurality of operations to the quantum mechanical system; for each of the plurality of operations, taking a single-qubit measurement of the quantum mechanical system, wherein each single-qubit measurement has a binary result; determining a plurality of measurement projectors corresponding to the plurality of single-qubit measurements; determining a probability for each of the plurality of measurement projectors; and reconstructing the quantum state of the system based on the probabilities and the measurement projectors; wherein reconstructing the quantum state is performed in accordance with the following expression: ρ = ( 2 d ⁢ ∑ i = 1 d 2 - 1 ⁢ p i ⁢ P i + ( 1 - p i ) ⁢ ( 1 - P i ) ) - ( d 2 - 2 d ) ⁢ I d , where d is the dimension of the quantum mechanical system, ρ is the state of the quantum mechanical system, I d denotes the identity operator, P i is one of the plurality of measurement projectors, and p i is the probability for the measurement projector P i .