{"id":303,"date":"2023-06-09T12:05:34","date_gmt":"2023-06-09T10:05:34","guid":{"rendered":"https:\/\/logbooks.ifosim.org\/finesse\/?p=303"},"modified":"2024-08-07T20:13:42","modified_gmt":"2024-08-07T18:13:42","slug":"balanced-homodyne-detection-workaround","status":"publish","type":"post","link":"https:\/\/logbooks.ifosim.org\/finesse\/2023\/06\/09\/balanced-homodyne-detection-workaround\/","title":{"rendered":"Balanced homodyne detection workaround"},"content":{"rendered":"\n<p>At the time of writing this entry, the way to do balanced homodyne detection is not yet fully implemented in Finesse3 as the example shows it <a href=\"https:\/\/finesse.ifosim.org\/docs\/latest\/examples\/07_homodyne.html\">here<\/a>. The issue is the -3dB limitation of the squeezing level which comes from the fact that the beamsplitter is 50\/50, so half of squeezing is lost before reaching the qnoised. When I try to put a qnoised at each output port of the HD, I cannot substract the quantum noise from both detectors and get convincing results. After discussing with Dan, it seems that the readout_dc does not handle operations on quantum noise yet either.<\/p>\n\n\n\n<p>There is however a workaround to measure the correct level of squeezing in the current configuration by decreasing the level of squeezing that is lost on the unused output port of the BS and increasing the LO power as a consequence : <\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>import finesse\nimport numpy as np\nimport matplotlib.pyplot as plt\nfinesse.configure(plotting=True)\n\nkat = finesse.Model()\nkat.parse(\n    \"\"\"\n    l l1 P=1e6\n    s s1 l1.p1 bs1.p4 L=1\n    sq sq1 db=10\n    s s2 sq1.p1 bs1.p1\n    bs bs1 T=1e-6 L=0 alpha=45\n\n    # Set a signal frequency to activate the signal simulation\n    # (needed for squeezing effects to be observed)\n    fsig(1)\n\n    # Output the pure shot noise along with the qnoised detector\n    # measuring the effects of the squeezing\n    qnoised sqzd_noise bs1.p2.o\n    qshot shot_noise bs1.p2.o\n\n    xaxis(l1.phase, lin, -90, 90, 360)\n    \"\"\"\n)\n\n# run the script\nout = kat.run()\n\n# plot the solution in squeezing dB scale\nplt.plot(out.x&#91;0], 20*np.log10(out&#91;'sqzd_noise']\/out&#91;'shot_noise']))\nplt.xlabel('Local oscillator phase &#91;degrees]')\nplt.ylabel('Squeezing level &#91;dB]')<\/code><\/pre>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>At the time of writing this entry, the way to do balanced homodyne detection is not yet fully implemented in Finesse3 as the example shows it here. The issue is the -3dB limitation of the squeezing level which comes from the fact that the beamsplitter is 50\/50, so half of squeezing is lost before reaching [&hellip;]<\/p>\n","protected":false},"author":90,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ssl_alp_hide_revisions":false,"footnotes":"","ssl_alp_hide_crossreferences_to":false},"categories":[1],"tags":[],"ssl-alp-coauthor":[63],"class_list":["post-303","post","type-post","status-publish","format-standard","hentry","category-uncategorised"],"_links":{"self":[{"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/posts\/303","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/users\/90"}],"replies":[{"embeddable":true,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/comments?post=303"}],"version-history":[{"count":2,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/posts\/303\/revisions"}],"predecessor-version":[{"id":375,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/posts\/303\/revisions\/375"}],"wp:attachment":[{"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/media?parent=303"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/categories?post=303"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/tags?post=303"},{"taxonomy":"ssl-alp-coauthor","embeddable":true,"href":"https:\/\/logbooks.ifosim.org\/finesse\/wp-json\/wp\/v2\/ssl-alp-coauthor?post=303"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}