Joint measurement of electron spin qubits via proximal conductance

We propose a method to carry out joint measurements on spin qubits that are separated by several microns. Joint measurements, which reveal multi-qubit properties without determining anything about the individual qubits, are a key ingredient to performing quantum error correction and to producing measurement-based entanglement of non-interacting qubits. We presume that the qubits are capacitively coupled to a common conductance channel and are separated by a distance less than the phase coherence length of the semiconductor, and we calculate the tolerance of the procedure to various experimental imperfections. Conditions for carrying out $N$-qubit syndrome measurements are discussed.