Nonuniversal conductance quantization in high-quality quantum wires

We present a theoretical analysis of recent experimental results of Yacoby et al. on transport properties of high-quality quantum wires. We suggest an explanation of observed deviations of the conductance from the universal value ${2e}^2/h$ per channel in the wire. We argue that at low temperatures and biases the deviation can be a consequence of anomalously enhanced backscattering of electrons entering the two-dimensional electron gas from the wire and is not connected to intrinsic properties of a one-dimensional electron gas.