The following experiment is not too exciting, but shows all of these basic steps in the simplest possible way.\u00a0Figure 121a\u00a0shows the system we used in chapter 2 to detect single photons (Figure 33), to which we have added two pieces of polarizing film. Now, remember that the previous polarization of a photon exiting a polarizer is not important, but its polarization is instead reset to the polarizer\u2019s angle (Figure 121b). Therefore, the first polarizer causes all photons entering the system to be polarized at 45\u00b0. In quantum physics experiments, this process is thought of as\u00a0preparing<\/em>\u00a0the photon\u2019s quantum state to a 50%\/50% superposition of 0\u00b0 and 90\u00b0 polarizations. The photon is then allowed to spend some time in this superposition of quantum states until its quantum state collapses when a\u00a0measurement<\/em>\u00a0is made by the analyzing polarizer and PMT. The analyzer is simply a second piece of polarizing film placed within a mount that allows it to rotate (we used a Thorlabs CLR1 SM1-compatible rotatable mount). If a photon exits the analyzing polarizer, it is detected by the PMT (of course, taking into account the absorption of the bandpass filters and quantum efficiency of the PMT).<\/p>\n\n\n\n Figure 121\u00a0A basic quantum physics experiment consists of preparing a quantum state, allowing the state to evolve, and then conducting a measurement to collapse the system into a state that can be detected.\u00a0(a)<\/strong>\u00a0In this simple setup, the polarization of photons is set to 45\u00b0, which is a 50%\/50% superposition of polarization states at 0\u00b0 and 90\u00b0. Photons spend some time as they traverse the flight tube in a superposition of quantum states until their polarization collapses when they reach the measurement instrument comprising the \u201canalyzer\u201d (another piece of polarizing film) and PMT.\u00a0(b)<\/strong>\u00a0The important thing to remember is that a polarizer doesn\u2019t simply allow a photon to pass or not pass, but rather sets the polarization of photons that manage to pass through the polarizer.\u00a0(c)<\/strong>\u00a0Looking at the process one photon at a time, the first polarizer prepares the photon\u2019s quantum state, while the second polarizer (the analyzer), along with the detector, conducts the measurement. The process is commonly repeated many times to determine the probability of occurrence for each possible outcome of the experiment. What is important to understand is that, from the second polarizer\u2019s point of view, the photon has two possible polarization states: (1) the photon has the same polarization as the analyzer and can thus go through, or (2) the photon\u2019s polarization is orthogonal to that of the polarizer and should be absorbed. The angle between the first and second polarizer only changes the probability of occurrence of each possible outcome. Once detected by the PMT, the collapse finalizes, and we either detect or don\u2019t detect the presence of a photon. Do you see how this experiment is analogous to the Schr\u00f6dinger\u2019s Cat gedankenexperiment<\/em> (thought experiment)?<\/p>\n\n\n\n As we will see in the following sections and in chapter 8, the whole field of experimental quantum physics, as well as all of the modern technologies of quantum teleportation, quantum cryptography, and others follow the basic protocol of preparing a quantum state, allowing the state to evolve, and finally performing a measurement. Of course, what differentiates each experiment is how the quantum state is prepared, as well as the things that you can do to a particle in superposition of states without causing collapse of its wavefunction.<\/p>\n","protected":false},"excerpt":{"rendered":" It is very important to remember that Schr\u00f6dinger\u2019s cat thought experiment was proposed as an absurd extrapolation of the Copenhagen Interpretation. Although we are ignorant about the boundary between quantum and classical systems, quantum physics has very little to do with cats or any other macroscopic system. For all of the reasons that we have […]<\/p>\n","protected":false},"author":1,"featured_media":4199,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[517],"tags":[],"class_list":["post-4459","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-schrodinger-and-his-zombie-cat"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/09\/3d-1.png","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4459","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=4459"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4459\/revisions"}],"predecessor-version":[{"id":4460,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4459\/revisions\/4460"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/4199"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=4459"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=4459"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=4459"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/learning.oreilly.com\/api\/v2\/epubs\/urn:orm:book:9781118170700\/files\/OEBPS\/images\/185-1.jpg\")
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