We propose and realize a transistor-like superconducting circuit including two serially connected segments of a narrow nanowire joint by a wider segment with a capacitively coupled gate in between. This circuit is made of amorphous NbSi film and embedded in a network of Cr microresistors ensuring high external impedance and therefore, as predicted by Mooij and Nazarov, a coherent transfer of single Cooper pairs. Virtual quantum phase slips in two narrow segments of the wire lead in this case to quantum interference of voltages on these segments making this circuit dual to the dc SQUID. Our samples demonstrated appreciable Coulomb blockade voltage (analog of critical current of the SQUID) and remarkable periodic modulation of this blockade by an electrostatic gate (analog of flux modulation in the SQUID). The obtained experimental results and the model of this QPS transistor will be discussed.