Kerr-cat case approves #173
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| a squeezing drive and three-wave mixing. | ||
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| ## The device | ||
| The device that was used was a SNAIL with a planar resonator for readout. Both of these are housed inside of a 3D cavity. |
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I would just add what SNAIL means for ignorant people like me :)
| separated by an energy barrier. The two coherent states existing in these minima are |$\alpha$ $>$ and | ||
| |$-\alpha$ $>$, and the superposition of these coherent states form cat states. The Bloch sphere of this |
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I believe there is '$' mismatch
This should work: "$|\alpha>$" and "$|-\alpha>$"
| representations are sketched. Here, |$\pm$ $Z$ $\>$ = |$C^{\pm}\_{\alpha}$ $\>$ = (|+$\alpha$ $\>$ $\pm$ |-$\alpha$ $\>$)/$\sqrt{2}$ | ||
| and |$\pm Y$ $\>$ = |$C^{\mp i}_{\alpha}$ $\>$ = (|$+\alpha$ $\>$ $\mp$ $i$|$-\alpha$ $\>$)/$\sqrt{2}$. The continuous $X(\theta)$ gate |
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Same "$" mismatch here
| Cat quadrature readout (cqr) is a Quantum non-Demolition (QND) technique to readout the Kerr-cat qubit. | ||
| Thanks to the three-wave mixing of the SNAIL, a cqr pulse sent to it at $\omega_{resonator}$ - $\omega_{s}/2$ creates a | ||
| coherent drive in the readout resonator that we can measure. Figure 2 and 3 show the IQ-blobs | ||
| of the coherent states |$\alpha$ $>$ and |-$\alpha$ $>$ and the pulse sequence, respectively. |
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Same "$" mismatch here
| ## Cat quadrature readout | ||
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| Cat quadrature readout (cqr) is a Quantum non-Demolition (QND) technique to readout the Kerr-cat qubit. | ||
| Thanks to the three-wave mixing of the SNAIL, a cqr pulse sent to it at $\omega_{resonator}$ - $\omega_{s}/2$ creates a |
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What is omega_s here?
| delay, and (v) apply a second cqr pulse. This pulse sequence is repeated N times to get good SNR. | ||
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| The experimental data can be seen in Fig. 4, and by fitting it to single exponential decay we find | ||
| $\tau_{\alpha} = 163 \mu s$ and $\tau_{-\alpha} = 164 \mu s$. |
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Can we compare these values to the coherence time of the standard fock states to emphasize the improvement?
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| **Figure 5**, cartoon of the pulse sequence for measuring the lifetime during free evolution. | ||
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| The main lines of QUA code that produce Fig. 4 are shown below. The QUA code that reproduces the data is `T_coh_free_decay.py`. |
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I think that the python file is missing
| ## Coherence times while continuous measuring | ||
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| Figure 6 and 7 we show the lifetimes and pulse sequence of the |$\alpha$ $>$ and |$-\alpha$ $>$ states while | ||
| continoulsy performing measurements to the qubit. The lifetimes are smaller due to the non-perfect QNDs of |
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Is there a reason to measure continuously from the physics standpoint or is it just to quantify the QND imperfection and show how to do it in QUA?
| play('ftc_rise', 'squeeze_rise') | ||
| align('squeeze_rise', 'squeeze_drive') | ||
| play('cw', 'squeeze_drive', duration=int(4e6//4)) | ||
| align('squeeze_drive', 'squeeze_fall') | ||
| play('ftc_fall', 'squeeze_fall') |
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Here you split the pulse into three parts because you want to control the flat length without stretching the rise and fall parts, right?
If you do it with a single element you end up having gaps?
| coherent drive in the readout resonator that we can measure. Figure 2 and 3 show the IQ-blobs | ||
| of the coherent states |$\alpha$ $>$ and |-$\alpha$ $>$ and the pulse sequence, respectively. | ||
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Was it acquired with the OPX or does it come from the paper?
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@KevinAVR What is the status of this? |
These are experiments I did at Devoret's lab last year, and now the people pparoved it as it to go to our github