Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High-fidelity qubit readout using interferometric directional Josephson
  devices   Nonreciprocal microwave devices, such as circulators and isolators, are
needed in high-fidelity qubit readout schemes to unidirectionally route the
readout signals and protect the qubits against noise coming from the output
chain. However, cryogenic circulators and isolators are prohibitive in scalable
superconducting architectures because they rely on magnetic materials. Here, we
perform a fast (750 ns) high-fidelity (95%) quantum nondemolition readout of a
coherent superconducting qubit ($T_{1}=52$ $\mu s$, $T_{\rm{2E}}=35$ $\mu s$)
without any nonreciprocal magnetic devices. We employ in our readout chain a
microwave-controlled qubit-Readout Multi-Chip Module (qRMCM) that integrates
interferometric directional Josephson devices consisting of an isolator and a
reconfigurable isolator/amplifier device and an off-chip low-pass filter. Using
the qRMCM, we demonstrate isolation up to 45 dB within 13 MHz, when both
directional devices are operated as isolators, and low-noise amplification in
excess of 10 dB within a dynamical bandwidth of $10$ MHz, when the
reconfigurable device is operated as an amplifier. We also demonstrate using
the variable isolation of the qRMCM an in-situ enhancement of the qubit
coherence times $T_{\rm{\varphi}}$ and $T_{\rm{2E}}$ by two orders of magnitude
(i.e., from $T_{\rm{\varphi}}=T_{\rm{2E}}=0.5$ $\mu s$ to $T_{\rm{\varphi}}=90$
$\mu s$ and $T_{\rm{2E}}=50$ $\mu s$). Furthermore, by directly comparing the
qRMCM performance to a state-of-art configuration (with $T_{\rm{2E}}\approx
2T_{1}$) that employs a pair of wideband magnetic isolators, we find that the
excess pure dephasing measured with the qRMCM (for which $T_{\rm{2E}}\approx
T_{1}$) is likely limited by residual thermal photon population in the readout
resonator. Improved versions of the qRMCM could replace magnetic circulators
and isolators in large superconducting quantum processors.

22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
3
The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: econ
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph