arXiv subjects

Siyuan Han

Publications and source records attributed to Siyuan Han.

58 records · Page 4Linked to original sources

arXiv2002

Error prevention scheme with two pairs of qubits

A scheme is presented for protecting one-qubit quantum information against decoherence due to a general environment and local exchange interactions. The scheme operates essentially by distributing information over two pairs of qubits and through error prevention procedures. In the scheme, quantum information is encoded through a decoherence-free subspace for collective phase errors and exchange errors affecting the qubits in pairs; leakage out of the encoding space due to amplitude damping is reduced by quantum Zeno effect. In addition, how to construct decoherence-free states for n-qubit information against phase and exchange errors is discussed.

quant-ph↗

arXiv2002

Error correction code for protecting three-qubit quantum information against erasures

We present a quantum error correction code which protects three quantum bits (qubits) of quantum information against one erasure, i.e., a single-qubit arbitrary error at a known position. To accomplish this, we encode the original state by distributing quantum information over six qubits which is the minimal number for the present task (see reference [1]). The encoding and error recovery operations for such a code are presented. It is noted that the present code is also a three-qubit quantum hidded information code over each qubit. In addition, an encoding scheme for hiding $n$-qubit quantum information over each qubit is proposed.

quant-ph↗

arXiv1999

Observation of Coherent Charge-State Mixing in Asymmetric Bloch Transistors

The reduced switching current of an excited energy-band in a Bloch transistor can be used to detect microwave-induced interband transitions. Spectroscopic measurements of the band-gap are performed by mapping the frequency dependence of the excitation threshold where the microwave photon energy and band-gap are equal. This excitation threshold also provides a probe of charge-state mixing on the island of the transistor. Any asymmetry in the junctions of the transistor makes the coherent mixing of charge-states appear as a finite gap-splitting at the electrostatic degeneracy point between states differing by one excess Cooper-pair on the island. The measured gap-splitting in an asymmetric transistor clearly demonstrates the effect.

cond-mat.mes-hall↗

arXiv1998

Observation of Strong Coulomb Blockade in Resistively Isolated Tunnel Junctions

We report measurements of the Coulomb-blockade current in resistively isolated (R_{Isol} >> h/e^{2}) tunnel junctions for the temperature range 60mK $We report measurements of the Coulomb-blockade current in resistively isolated ($R_{Isol}\gg h/e^{2})$ tunnel junctions for the temperature range 60mK < T < 230mK where the charging energy E_{c} is much greater than the thermal energy. A zero-bias resistance R_{0} of up to 10^{4}R_{T} (the tunnel resistance of the bare junction) is obtained. For eV << E_{c}, the I-V curves for a given R_{Isol} scale as a function of V/T, with I \propto V^{α(R_{Isol})} over a range of V. The data agree well with numerical calculations of the tunneling rate that include environmental effects.

cond-mat.mes-hall↗