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John Preskill on Quantum Computing
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John Preskill - https://twitter.com/preskill - is a theoretical physicist and the Richard P. Feynman Professor of Theoretical Physics at Caltech - http://www.theory.caltech.edu/people/preskill/ Read the transcript here - https://blog.ycombinator.com/john-preskill-on-quantum-computing He once won a bet with Steven Hawking - http://www.theory.caltech.edu/people/preskill/bets.html - which as he writes made him “briefly almost famous.” John and Kip Thorne - https://en.wikipedia.org/wiki/Kip_Thorne - bet that singularities could exist outside of black holes and after six years Hawking conceded that they were possible in very special, “nongeneric” conditions. In this episode we cover what John’s been focusing on for years: quantum information, quantum computing, and quantum error correction. The YC podcast is hosted by Craig Cannon - https://twitter.com/craigcannon
Segments Timeline
The Birth of Quantum Computing
John Preskill discusses the origins of quantum computing, highlighting Richard Feynman's pivotal role in proposing that quantum systems could simulate nature more effectively than classical computers. He explains how Feynman's experiences during World War II and his interest in particle physics led to the realization that quantum mechanics could be harnessed for computation, setting the stage for the development of quantum computers.
"and what was the revelation that made made scientists and physicists think that a quantum computer could exist it's not obvious you know a lot of people thought he couldn't okay the idea that a quantu..."
Quantum Error Correction Explained
Preskill introduces the concept of quantum error correction, explaining its significance in protecting quantum information from environmental disturbances. He describes how encoding information in entangled states can safeguard it, even when interactions with the environment occur, making quantum error correction a crucial aspect of practical quantum computing.
"computer and the idea caught on about ten years later when Peter shor made the suggestion that we could solve problems which don't seem to have anything to do with physics which are really things abou..."
Understanding Quantum Entanglement
In this segment, Preskill elaborates on quantum entanglement, illustrating how it differentiates quantum systems from classical ones. He uses the analogy of a book to explain how information is stored in the correlations between quantum states, emphasizing that observing individual parts does not reveal the whole system's information, which is essential for quantum error correction.
"has become something you can do in the lab yeah and how does quantum error correction work I've seen a bunch of diagram so maybe this is difficult to explain but how would you explain it well I would ..."
Grover's Algorithm and Quantum Search
Preskill explains Grover's algorithm, which enhances the efficiency of searching through possibilities in quantum computing. He discusses its application to complex problems like the Traveling Salesman problem, highlighting how quantum computing can speed up exhaustive searches and improve the chances of finding optimal solutions through quantum interference.
"a system of many particles mm-hmm and the environment is kind of kicking them around it's interacting with them because you you can't really completely turn off those interactions no matter how hard y..."
The Future of Quantum Computing
Preskill reflects on the potential transformative impact of quantum computing on society. He emphasizes that quantum computers will not merely be faster classical computers but will revolutionize information processing. He speculates on their applications in material science and pharmaceuticals, suggesting that quantum computing could lead to breakthroughs in understanding complex quantum systems.
"what's quantum about grover it takes advantage of the property in quantum physics that probabilities might tell me if I'm getting too inside Bassman Oh perfect that probabilities are the squares of am..."
Challenges and Opportunities Ahead
In this concluding segment, Preskill discusses the challenges of predicting the future of quantum computing. He acknowledges the limitations of current understanding and the potential for unexpected applications that could arise. He emphasizes the importance of continued research and exploration in quantum physics to unlock the full potential of quantum computing.
"computing the ones which will affect everyday life I think are better methods for understanding and inventing new materials new chemical compounds mm-hmm things like that can be really important you k..."
Current State of Quantum Computing Hardware
In this segment, Preskill outlines the current landscape of quantum computing hardware development. He notes the various approaches being explored and the challenges in determining which will be the most effective for scalability, while also discussing the anticipated advancements in qubit technology.
"problem actually we don't know how to prove that from first principles maybe somebody will come away you know come along one day and figure out how to solve factoring very fast on a digital computer i..."
Key Problems in Quantum Computing
Preskill addresses pressing issues in quantum computing that need resolution for the field to advance. He discusses the importance of improving qubit technology and error rates, and how these improvements could enable more complex computations that are currently unattainable.
"about yeah so so maybe we should jump to one of the questions from Twitter which is related to that so Travis Shelton asked what are the most problem pressings in physics let's say specifically around..."
The Role of Qubit Quality
This segment focuses on the significance of qubit quality in quantum computing. Preskill explains how error rates in quantum gates affect computational capabilities and the importance of achieving better qubit performance to enhance the reliability of quantum computations.
"people care about well let's go over where we are now yeah definitely okay so people have been working on quantum hardware for you know 20 years working hard and there are a number of different approa..."
Hybrid Approaches to Quantum Optimization
Preskill discusses the potential of hybrid classical-quantum methods for optimization problems. He emphasizes the need for effective feedback mechanisms in quantum computing to improve results and the challenges posed by current qubit imperfections.
"so are doing something that's kind of super classical yeah at least we don't know how to do exactly the same things with ordinary computers now that doesn't mean they'll be able to do anything that's ..."
Advancements in Quantum Control Techniques
In this segment, Preskill elaborates on the various techniques being developed to control qubits effectively. He highlights the importance of achieving precise interactions between qubits and the challenges posed by environmental factors that can disrupt quantum states.
"below you know an error every hundred gates so that if you have a circuit with a thousand cubits there's a lot of noise so exactly like it does for instance a hundred qubit quantum computer really mea..."
Superconducting Circuits vs. Trapped Ions
Preskill compares two leading quantum computing technologies: superconducting circuits and trapped ions. He discusses their respective advantages and challenges, emphasizing the need for continued exploration of different hardware approaches to find the most effective solutions.
"that's equally important so anyway coming back to Travis's question well there are lots of things yeah that we'd like to be able to do better but just having much better qubits would be huge right so ..."
The Future of Quantum Computing
Preskill speculates on the future of quantum computing, discussing the potential for breakthroughs in qubit technology and the implications for computational power. He emphasizes the importance of ongoing research and development to overcome current limitations.
"and you don't you don't worry about the it's gotten to the point where there is some error protection built in at a hardware level okay in a processor because I mean we're doing these crazy things lik..."
Engineering Strategies for Quantum Success
In this segment, Preskill addresses various engineering strategies being pursued in quantum computing. He highlights the importance of coherence times and the need for better materials and fabrication techniques to enhance the performance of quantum systems.
"them to interact I mean we have this set of desiderata which are kind of in tension with one another on the one hand we want to isolate the qubits very well yeah on the other hand we want to control t..."
Topological Quantum Computing
Preskill introduces the concept of topological quantum computing, a promising approach being explored by Microsoft. He discusses its potential advantages in qubit control and the ambitious goals of this research direction, while acknowledging the challenges that lie ahead.
"thinking about it yeah suppose you have a little loop of wire and there's current flowing in the loop it's a superconducting wire so it just keeps flowing normally there'd be resistance which would di..."
The Importance of Coherence Time
Preskill emphasizes the critical role of coherence time in quantum computing. He explains how longer coherence times can improve qubit performance and the ongoing advancements in this area, which are essential for the future success of quantum technologies.
"validated qubit of this type soon maybe next year okay and then I nobody really knows where it goes from there but suppose it's the case that you could do a two qubit gate with an error rate of 1 mill..."
Evaluating Quantum Computing Approaches
In the final segment, Preskill evaluates different quantum computing approaches and their potential for success. He discusses the current leaders in the field and the factors that will determine which technologies will prevail in the coming years.
"that that type of progress better materials better fabrication better control the way you control these things is with microwave circuitry not that different from you know the kind of things that are ..."
The Future of Quantum Computing Technologies
Preskill elaborates on the advantages of superconducting circuits, including their speed and scalability compared to trapped ions. He also discusses the potential of electron spins in silicon technology and the uncertainty surrounding which quantum computing technology will ultimately prevail.
"interesting okay but I for the near term the most advanced are superconducting circuits and trapped ions which is why I mentioned those first and I think that will remain true you know over the next f..."
Quantum Computing in the Cloud
Preskill envisions a future where quantum computers are accessed via the cloud, similar to AWS. He discusses the importance of user-friendly interfaces that allow individuals to utilize quantum computing without needing to understand the underlying physics.
"that can change and I mean that from a theorist perspective this topological approach is very appealing and so we could imagine you know it takes off maybe ten years from now and it becomes the leader..."
Nuclear Spins and Quantum Smart Cards
Preskill introduces the concept of using nuclear spins for quantum information storage, which could potentially operate at room temperature. He speculates on the future of quantum smart cards that could enhance security in banking transactions.
"yeah it seemed I think that that's how it will be in the near term I think you you're not going to have most of us won't have a quantum computer you know sitting on your desktop or in your pocket mayb..."
Quantum Threats to Current Encryption
Preskill addresses the risks quantum computers pose to current encryption schemes, particularly public key cryptography. He explains how quantum computers could efficiently break widely used systems like RSA and elliptic curve cryptography, necessitating new security measures.
"times and you know if you're if you go to the ATM and you're worried that there's a rogue Bank it's gonna steal your information one solution to that problem I'm not saying there aren't other solution..."
Post-Quantum Cryptography Solutions
Discussing the need for post-quantum cryptography, Preskill outlines two main approaches: developing new cryptographic protocols resistant to quantum attacks and utilizing quantum communication for enhanced privacy. He emphasizes the urgency of addressing these challenges.
"so RSA which is one of the ones that's widely used mmm-hmm as typically practiced today the to break it you'd have to do something like factor a number which is over 2,000 bits long to 2048 and that's..."
Quantum Key Distribution Explained
Preskill explains the concept of quantum key distribution, highlighting its advantages over traditional methods. He describes how quantum properties can ensure secure key exchange and the infrastructure required for effective implementation.
"that it's really hard for a quantum adversary that we're all going to switch over but it's certainly time to be thinking about it you know when people worry about the privacy of course different users..."
Challenges in Quantum Communication
Preskill discusses the challenges of scaling quantum communication over long distances, emphasizing the need for quantum repeaters and error correction. He outlines the current capabilities and future potential of sending quantum information through optical fibers.
"the idea of what we call quantum key distribution which is a particular type of quantum cryptography is that I can actually send you the key or you can send me your key but why can't any eavesdropper ..."
Quantum Sensing and Future Applications
Preskill highlights the potential of quantum technology beyond computing, particularly in sensing applications. He discusses the implications for biological and medical fields, emphasizing the need for improved sensors capable of monitoring molecular behaviors.
"future of privacy that people are interested in and does that necessitate quantum computers on both ends - yes but not huge ones okay and the reason well yes and no okay at the scale of tens of kilome..."
John Preskill's Journey in Physics
Preskill shares his background in physics, detailing his transition from elementary particle theory to quantum computing. He reflects on the challenges of integrating gravity with quantum mechanics and his ongoing interest in these fundamental questions.
"me um change direction a little yeah from what we've been talking about so far well let me tell you a little bit about me sure so I didn't start out interested in information yeah a career you know I'..."
Exploring Space-Time Geometry
Preskill delves into the relationship between quantum entanglement and the geometry of space-time. He posits that the structure of space may emerge from quantum correlations, challenging traditional notions of geometry. This segment discusses the implications of quantum error correction in understanding space-time and how entanglement could be the key to maintaining the integrity of space.
"you know many decades and then I kind of got sidetracked because I got excited about quantum computing but you know I I've always looked at quantum information not just as a technology you know I'm a ..."
The Challenge of Quantum Research
John Preskill addresses the complexities of researching quantum entanglement and space-time geometry. He acknowledges the difficulties in obtaining experimental guidance for these concepts and the audacity required to tackle such profound questions. This segment highlights the potential for future experiments with quantum computers to provide insights into the nature of space-time.
"relatively near term mmm-hmm when we have a hundred qubits you know there are some things that we can do to understand the behavior of the dynamics of you know a highly complex system of 100 qubits th..."
Entanglement and Space Integrity
In this thought-provoking segment, Preskill explains how entanglement is crucial for the stability of space. He discusses the hypothetical consequences of breaking entanglement between parts of space and how this could lead to a disconnection of space itself. This exploration of entanglement's role in maintaining the fabric of space-time is a key insight into quantum physics.
"what is that we think it's quantum entanglement that you can think of the geometry as arising from quantum correlations among parts of a system and that's really what defines who's close to who and so..."
Building a Laboratory Space-Time
Preskill shares his vision of creating a 'toy space-time' in the laboratory using highly entangled quantum systems. He discusses how these systems could help researchers understand the principles of quantum entanglement and space-time geometry. This segment emphasizes the potential of quantum technologies to simulate complex systems that classical computers cannot handle.
"know we're trying to get a deeper grasp of what that means and how do you make any progress on that that seems like the most unbelievably difficult problem to work on it's difficult yeah as well for a..."
Misconceptions About Quantum Computing
In this segment, Preskill clarifies common misconceptions about quantum computing, particularly regarding superposition and entanglement. He explains the importance of interference in quantum algorithms and how it differs from classical computation. This discussion sheds light on the unique capabilities of quantum computers and the challenges they present.
"would help us to understand the basic principles better wildd yeah desktop space-time seems pretty cool yeah it's pretty fundamental we didn't really talk about what people sometimes we didn't implici..."
Collaborating with Richard Feynman
John Preskill reflects on his time at Caltech and his interactions with the legendary physicist Richard Feynman. He shares insights into their shared interests in fundamental interactions and quantum chromodynamics. This segment provides a personal glimpse into Preskill's academic journey and the influence of Feynman on his work.
"read it out you're you know there's a limited amount of information you can get you're not going to be able to read out the results of some huge number of computations in a single shot measurement so ..."
Feynman's Unique Approach to Physics
In this segment, John Preskill discusses Feynman's distinctive style of thinking and problem-solving. He notes Feynman's tendency to rely on his own insights rather than established literature, which led to fascinating discussions and a unique perspective on physics.
"arrived at Caltech that was 1983 Fineman was born in 1918 so he was 65 I'm 64 now so maybe he wasn't so old but at the time he seemed pretty ancient to me yeah since I was thirty okay and those who in..."
Feynman's Storytelling and Interests
Preskill describes Feynman's love for storytelling and his diverse interests beyond physics, including biology and computation. He recalls Feynman's excitement about technology, particularly his first IBM PC, and how it reflected his curiosity about the world.
"didn't tell him dick you should read this paper by Polyakov well maybe I did I wouldn't even heard that because he saw that problem that your yang about yeah but I knew what poly coffin said about it ..."
Making Quantum Computing Accessible
John Preskill discusses the potential for quantum computing to become more accessible to younger generations. He envisions a future where children engage with quantum concepts through games, making the counterintuitive nature of quantum mechanics more familiar.
"on the Challenger Commission after the Space Shuttle blew up and so he was in in Washington a lot of the time but he had come back from time to time and he would sort of you know sit back and relax in..."
The Role of STEM Education in Democracy
Preskill emphasizes the importance of STEM education in fostering critical thinking and reasoning skills among the general population. He argues that understanding evidence and reasoning is crucial for making informed decisions in a democratic society.
"you know that opens the opportunity to for trying things out and see what happens mm-hmm and after you played the game enough you you start to anticipate actually it's an important point about the app..."
The Need for Scientists in Government
In this segment, Preskill discusses the importance of having scientifically trained individuals in government. He highlights examples of physicists in Congress and their positive influence on science policy, advocating for more representation of scientific expertise in political decision-making.
"that there are some things that if you're a person with some it doesn't necessarily have to be technical but if you're used to evaluating evidence and making a judgement based on that eminence about w..."
The Emergence of Quantum Valley
Preskill explores the concept of a 'Quantum Valley' akin to Silicon Valley, noting the rise of quantum startups in the Bay Area. He discusses the concentration of tech industry resources and talent in this region, which fosters innovation in quantum computing.
"are and on the on the quantum side someone asks Vika scrod he asked where the quantum Valley might be do you have your thoughts as in Silicon Valley for quantum computing well I don't know but you loo..."
Advice for Aspiring Quantum Entrepreneurs
John Preskill offers advice for physicists looking to start their own companies in the quantum computing space. He emphasizes the importance of building a diverse team with various expertise to tackle the multifaceted challenges of quantum technology.
"now well then what about the the physicists who might be listening to this if they're thinking about starting a company mmm do you have advice for them just speaking very generally that if you're putt..."
The Power of Teaching in Science
Preskill reflects on the benefits of teaching as a means to deepen one's understanding of complex topics. He shares insights on how teaching can rejuvenate knowledge and enhance communication skills, making it a rewarding experience for scientists.
"things would you advise someone then to to maybe teach or you know try and explain it to I don't know they're young cousins because I I think like Fineman may be recognized as the king of communicatin..."
Recommended Resources for Learning Physics
Preskill recommends Leonard Susskind as a key communicator in physics, likening him to Richard Feynman. He discusses Susskind's lectures and books, particularly the 'Theoretical Minimum' series, as valuable resources for anyone interested in learning more about quantum physics.
"it you know um don't look at it as as a burden or you know some kind of task you have to do along with all the other things you're doing it should be a pleasure and when it's successful it's very grat..."
Transformative Learning Through Teaching
In this concluding segment, Preskill shares his personal journey of learning quantum computing through teaching. He reflects on how the interdisciplinary nature of quantum information has expanded his knowledge and understanding of complex scientific concepts.
"his ability to do that mm-hmm I need to subscribe actually here's a question man in in the things you've relearned while teaching over the past I guess it's over 35 years no is that right something li..."