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<p class="MsoNormal">The main practical difference is that their approach uses continuous variables, not discrete qubits. I can’t figure out exactly what they have managed to fabricate. There’s a group in Australia that does similar research, see _<i>Integrated
photonic platform for quantum information with continuous variables</i>_ vs. _<i>Continuous-variable gate decomposition for the Bose-Hubbard model</i>_.
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">Friam <friam-bounces@redfish.com> on behalf of Jochen Fromm <jofr@cas-group.net><br>
<b>Reply-To: </b>The Friday Morning Applied Complexity Coffee Group <friam@redfish.com><br>
<b>Date: </b>Sunday, January 27, 2019 at 4:40 AM<br>
<b>To: </b>The Friday Morning Applied Complexity Coffee Group <friam@redfish.com><br>
<b>Subject: </b>Re: [FRIAM] Quantum Computing<o:p></o:p></span></p>
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<p class="MsoNormal">Yes, the gate model is described in books like "Quantum Computation and Quantum Information" from Michael Nielsen. The theory from David Deutsch et al seems to be established. We have Shor's algorithm, Grover's algorithm and many others
but there still seems to be a significant gap between theoretical insights and experimental results. <o:p></o:p></p>
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<p class="MsoNormal">How do you program a AQC quantum computer? Somehow it must be setup to execute a certain type of calculation? <o:p></o:p></p>
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<p class="MsoNormal">And what do you think about photonic quantum computers? The Canadian company Xanadu from Toronto tries to go in this direction. <o:p></o:p></p>
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<p class="MsoNormal">https://www.xanadu.ai/<o:p></o:p></p>
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<p class="MsoNormal">-Jochen<o:p></o:p></p>
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<p class="MsoNormal"><span style="color:black">-------- Original message --------<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">From: Marcus Daniels <marcus@snoutfarm.com>
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<p class="MsoNormal"><span style="color:black">Date: 1/27/19 01:49 (GMT+01:00) <o:p>
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<p class="MsoNormal"><span style="color:black">To: The Friday Morning Applied Complexity Coffee Group <friam@redfish.com>
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Subject: Re: [FRIAM] Quantum Computing
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi Jochen,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">There are currently two main approaches to quantum computing. The first is called adiabatic quantum computing (AQC). Complexity enthusiasts that have followed the spin glass
literature will be familiar with Ising spin systems. AQC exploits the tendency of physical systems to go to low energy. It turns out that many kinds of operations can be implemented even with two body interactions. For example logic programs map to
Ising systems. In fact a former colleague of mine, Scott Pakin has implemented a Prolog interpreter for a quantum annealer. The reason to use a quantum annealer over a classical thermal annealer is essentially speed. An anneal can be repeated every tens
of microseconds. For sampling applications, like finding all the ways to solve an NP-hard constrained optimization problem with discrete variables, this is potentially a big win. Classical mixed-integer programming approaches can be fast to find local/global
optima, but may give a fragile picture of the fitness landscape. It is possible to use annealers to mimic materials, and study phenomenon like quantum phase transitions. Quantum tunneling and entanglement have been demonstrated using commercially-available
quantum annealers. <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">The other approach to quantum computing is the gate model. Here the idea is to compose together unitary operators. This model is less surprising from a from a (functional) programming
perspective: There are gates that feed into other gates kind of like classical circuits. This is a what IBM (and others) are trying to do, and the difficulty of the task is reflected by the fact they only have a handful of qubits. Estimates vary, but to
implement the error correction that would give reliability on-par with classical digital computers could take 1000-fold or even more redundancy. That’s to get _<i>one</i>_ good qubit at > 99.9% reliability.
<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">AQC doesn’t require the long coherence times (especially resistance to dephasing) that the gate model requires. Recently there’s been a middle ground declared called NISQ which
is trying to find algorithms (like annealing) that work on imperfect gate-model qubits.
<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">There are two popular foundational technologies for qubits, superconductors and ion traps. The tradeoff is essentially between latency and stability. Ion traps can maintain coherence
a long time, but are relatively expensive to configure. The system you mention from IBM is a the former. Superconductors typically operate near absolute zero (tens of mK) with many layers of protection from electromagnetic radiation and the Ion traps use
elaborate laser control systems. <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Quantum computing is not BS, but it is very hard to engineer these systems and there is a long road ahead to bring this technology to practitioners. The CMOS-based computing systems
we all use are a miraculous accomplishments of humans, and are easy to take for granted. One of the national labs here in New Mexico actually owns an AQC system.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Marcus<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Friam <friam-bounces@redfish.com> on behalf of Jochen Fromm <jofr@cas-group.net><br>
<b>Reply-To: </b>The Friday Morning Applied Complexity Coffee Group <friam@redfish.com><br>
<b>Date: </b>Saturday, January 26, 2019 at 3:23 PM<br>
<b>To: </b>The Friday Morning Applied Complexity Coffee Group <friam@redfish.com><br>
<b>Subject: </b>[FRIAM] Quantum Computing</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">What do you think of Quantum Computing, will it be successful? IBM just built the IBM Q System One...<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">https://youtu.be/LAA0-vjTaNY
<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">...while others make a strong case against it..<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">https://spectrum.ieee.org/computing/hardware/the-case-against-quantum-computing<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">..or even call it bullshit<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">https://scottlocklin.wordpress.com/2019/01/15/quantum-computing-as-a-field-is-obvious-bullshit/<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">What's your opinion? <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">-Jochen<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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