Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, 28006 Madrid, Spain.
Phys Rev Lett. 2012 Jun 22;108(25):257001. doi: 10.1103/PhysRevLett.108.257001. Epub 2012 Jun 18.
It has been predicted that superconducting junctions made with topological nanowires hosting Majorana bound states (MBS) exhibit an anomalous 4π-periodic Josephson effect. Finding an experimental setup with these unconventional properties poses, however, a serious challenge: for finite-length wires, the equilibrium supercurrents are always 2π periodic as anticrossings of states with the same fermionic parity are possible. We show, however, that the anomaly survives in the transient regime of the ac Josephson effect. Transients are, moreover, protected against decay by quasiparticle poisoning as a consequence of the quantum Zeno effect, which fixes the parity of Majorana qubits. The resulting long-lived ac Josephson transients may be effectively used to detect MBS.
据预测，由拓扑纳米线构成的超导结，其中包含马约拉纳束缚态（MBS），会表现出反常的 4π 周期约瑟夫森效应。然而，找到具有这些非传统性质的实验装置是一项严峻的挑战：对于有限长度的线材，由于具有相同费米子奇偶性的状态的交叉是可能的，所以平衡超导电流总是 2π 周期性的。然而，我们表明，这种反常现象在交流约瑟夫森效应的瞬态中仍然存在。瞬态由于量子扎诺效应而受到准粒子中毒的保护，量子扎诺效应固定了马约拉纳量子比特的奇偶性。由此产生的长寿命交流约瑟夫森瞬态可有效地用于检测 MBS。
