Update July 11, 2022
Quantum advantage? – the long road ahead to making a useful quantum computer.
• Wired > “Quantum Advantage Showdowns Have No Clear Winners” by Sophia Chen (July 11, 2022) – A series of recent experiments between quantum and classical computers shows the term’s ever-evolving meaning.
Each claim of quantum advantage has set off other researchers to develop faster classical algorithms to challenge that claim.
Original post February 19, 2022
So, how is quantum physics connected with quantum computing?
Ask people on the street “What is a quantum computer?” and you’ll likely get a variety of replies. Huh? Media buzz / hype, fiction / myths, degrees of reality / research. So, levels of understanding.
A “classic” 2021 Wired article  re Majorana fermions included a 2018 video of IBM’s Dr. Talia Gershon (Senior Manager, Quantum Research) explaining quantum computing to 5 different people: a child, teen, a college student, a grad student and a professional.
“5 levels” is a format referenced in other posts, but particularly noteworthy is Wired’s “5 levels” video series (16 episodes released 2017 – 2022).
• Wired > “Quantum Computing Expert Explains One Concept in 5 Levels of Difficulty” (Released on 06/25/2018)
Dr. Gershon uses some props: a model of a quantum computer aka “the chandelier” and spinning coins.
And she notes IBM’s Quantum Computing initiative and free cloud access to some current quantum computers. And an exciting technology future.
I don’t think you’re gonna have one in your dorm room anytime soon but you’ll have access to one. There’s three free quantum computers that are all sitting in this lab here that anyone in the world can access through the cloud.
You know now that everybody around the world can access a quantum computer through the cloud, people are doing all kinds of cool things. They’re building games. [Quantum pong?]
This is such an exciting time in the history of quantum computing. Only in the last couple years have real quantum computers become available to everyone around the world. This is the beginning of a many decade adventure where we’ll discover so many things about quantum computing and what it’ll do. We don’t even know all of the amazing things it’s gonna do. And to me that’s the most exciting part.
Quantum computing is a fascinating endeavor to engineer and develop applications which rely on quantum properties: “So superposition is one quantum property that we use, entanglement is another quantum property, and a third is interference.”
The quantum computing romance has begun – as Ray Bradbury noted in a 1971 panel discussion:
“I think it’s part of the nature of man to start with romance and build to a reality. In order to get the facts we have to be excited to go out and get them and there’s only one way to do that—through romance.”
 Wired > “Microsoft’s Big Win in Quantum Computing Was an ‘Error’ After All” (Feb 12. 2021)
Quantum computers are built from devices called qubits that encode 1s and 0s of data but can also use a quantum state called a superposition to perform math tricks not possible for the bits in a conventional computer. The main challenge to commercializing that idea is that quantum states are delicate and easily quashed by thermal or electromagnetic noise, making qubits error-prone [qubits’ flakiness].
Google, IBM, and Intel have all shown off prototype quantum processors with around 50 qubits, and companies including Goldman Sachs and Merck are testing the technology. But thousands or millions of qubits are likely required for useful work. Much of a quantum computer’s power would probably have to be dedicated to correcting its own glitches.
Microsoft has taken a different approach, claiming qubits based on Majorana particles will be more scalable, allowing it to leap ahead. But after more than a decade of work, it does not have a single qubit.
6 thoughts on “Quantum computing explained – 5 levels of difficulty”
This MIT Technology Review article discusses the mismatch between visions of quantum computing – theoretical (so-called “in principle”) demonstrations, research funding, company stock market valuations, and claims of commercial applications – and current realities. And uses analogies to early 1900’s vacuum tubes, the first transistor in 1947, and the Wright brothers’ 1903 Wright Flyer.
• MIT Technology Review > “Quantum computing has a hype problem” by Sankar Das Sarma  (March 28, 2022) – Quantum computing startups are all the rage, but it’s unclear if they’ll be able to produce anything of use in the near future.
 In his article, physicist Sankar Das Sarma, director of the Condensed Matter Theory Center at the University of Maryland, College Park, notes:
Although somewhat off topic for this post on Quantum computing, quantum sensors also rely on quantum error correction (QEC).
And the timing of (or delay between) “sensing” and QEC actions: “… different speeds in information acquisition … result in a distortion of the output.” A refined mathematical model of such QEC-induced bias might permit rectification [tweaking] in post-processing.
• Phys.org > “The side effects of quantum error correction and how to cope with them” by Andreas Trabesinger, ETH Zurich (April 6, 2022)
Here’s an interesting recap of the history of quantum computing and an outlook for cutting-edge quantum research.
• Caltech Magazine > “Quantum’s Hub: The Institute for Quantum Information and Matter (IQIM)” by Omar Shamout (Summer 2022) – Includes video by John Preskill, Caltech’s Richard P. Feynman Professor of Theoretical Physics.
Photo: Graham Carlow/IBM
Here’s a brief article about the state of quantum computing.
• Wired > “Quantum Computing Has a Noise Problem” by Amit Katwala (Jan 17, 2023) – Today’s devices can be thrown off by the slightest environmental interference.
This Wired article claims to discuss: “Everything you ever wanted to know about qubits, superpositioning, and spooky action at a distance.” Some historical recap (with a timeline jargon). Levels of understanding. Practical uses. Additional references.
So, here’s a “belly flop into the murky shallows of quantum computing 0.101.”
• Wired > “The WIRED Guide to Quantum Computing” by Tom Simonite & Sophia Chen (Feb 22, 2023) – It’s not productive (or polite) to ask people working on quantum computing when exactly those dreamy applications will become real.
Some progress in creating practical quantum bits.
• Phys.org > “Doubling a qubit’s life, researchers prove a key theory of quantum physics” by Yale University (March 23, 2023) – Michael Devoret’s group [applied physics lab] has managed to more than double the lifetime of quantum information – their error-corrected qubit lived for 1.8 milliseconds.
Bloch sphere, a geometrical representation of a qubit – a two-level quantum system. The probability amplitudes for the superposition state (ψ) are given by complex-number equations using angles θ and φ. Image credit: Wiki.
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