In this episode of All-In, quantum physicist John Martinis explains the core principles of quantum mechanics and its departure from classical physics. He discusses how particles can exist in multiple states and exhibit wave-like properties, and describes the quantum tunneling phenomenon where particles pass through seemingly impassable barriers.
The conversation traces Martinis' research journey from his graduate work on macroscopic quantum effects to his development of superconducting qubits for quantum computers. He shares insights about the 2019 Google quantum supremacy experiment, where a 53-qubit system outperformed classical computers, and discusses the potential path toward million-qubit quantum computers through improved construction methods and AI-assisted error correction.

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Martinis and Friedberg explain that quantum mechanics is the mathematical theory governing particle behavior at atomic and subatomic scales. Unlike classical physics, quantum mechanics uses probability functions to describe particle locations and movements, with particles exhibiting wave-like properties and existing in multiple states simultaneously.
In discussing quantum tunneling, Martinis describes how particles can pass through seemingly impassable barriers when their wave functions extend through sufficiently thin obstacles. This phenomenon has practical implications for technology, particularly in memory circuits where electron tunneling can affect device functionality.
Martinis and his team investigated quantum behavior in macroscopic objects, particularly superconducting circuits containing billions of electrons and atoms. Using a Josephson device—two superconductors separated by an insulating barrier—coupled with a capacitor, they observed discrete energy levels similar to those seen in atomic physics. Their successful demonstration of quantum mechanics operating at a macro scale earned recognition in prestigious publications.
Martinis' career direction was significantly influenced by Richard Feynman's discussion of using quantum mechanics for computation. Following Feynman's vision, researchers like Peter Shor developed quantum algorithms capable of solving real-world problems. This theoretical foundation, combined with Martinis' experimental work, helped transform quantum computing from a concept into an active research field with commercial potential.
Building on his early experiments with quantum tunneling, Martinis helped develop superconducting qubits using Josephson junctions. His work culminated in the 2019 Google quantum supremacy experiment, where a 53-qubit system outperformed classical computers on specific tasks. Looking ahead, Martinis envisions developing million-qubit quantum computers through improved construction methods and AI-assisted error correction, aiming to solve problems beyond the capabilities of classical computers.
1-Page Summary
Quantum mechanics, defined by Martinis and Friedberg, is the mathematical theory that governs particle behavior at atomic and subatomic scales through probability functions, demonstrating puzzling phenomena like quantum tunneling.
Quantum mechanics departs from deterministic classical physics, using probabilities to describe potential locations and movements of particles at the atomic or smaller scale. Unlike objects visible to the human eye, subatomic particles are not governed by set paths.
Particles such as electrons display wave-like behaviors, forming standing waves around an atom's nucleus. Martinis refers to these electron waves as similar to musical tones produced by strings of different lengths and tensions. Friedberg describes the position and behavior of an electron not in terms of a fixed path but as a wave that denotes where it might be at any given time. Martinis notes that atoms are intrinsically quantum-mechanical, with a wave function that suggests electrons are somewhat "fuzzy" and exist in a probabilistic superposition, being "all around the nucleus at the same time."
Quantum mechanics reveals the phenomenon of quantum tunneling, which enables particles to overcome barriers that classical physics would consider absolutely impassable.
The concept of quantum ...
Fundamentals of Quantum Mechanics and Its Counterintuitive Properties
John Martinis has contributed significantly to the field of quantum mechanics by demonstrating that macroscopic objects exhibit quantum behavior, challenging the understanding of where the boundary lies between classical physics and quantum mechanics.
Martinis and his team investigated whether quantum mechanical behavior is observable in macroscopic objects such as superconducting circuits, which contain billions of electrons and atoms.
He mentioned the role of superconducting magnets in MRI machines, where the patient is essentially inside a super cooled magnet with a lasting magnetic field. Regarding his experimentation, Martinis posed the question of whether such macroscopic objects would obey quantum mechanics. The research focused on an electrical oscillator system to determine if it would display quantum mechanical nature or classical physics. Martinis' work provides an example of an electrical circuit that shows collective quantum behavior, which indicates macroscopic quantum effects in the motion of electrons within superconducting circuits.
Furthermore, Martinis examined the behavior of currents and voltages in an electrical circuit, observing that measurements in such systems could lead to a probabilistic state change due to quantum effects. This phenomenon draws parallels to the famed Schrödinger's Cat paradox, which illustrates the peculiarities of quantum superposition.
Martinis described his early work with a rudimentary circuit using analog simulators to gather data. His research involved using a Josephson device or electrical circuit, operating at microwave frequencies, to increase the chance of observing quantum phenomena. By applying his understanding of the Josephson junction—two superconductors separated by an insulating barrier where Cooper pairs tunnel through without loss—he found that t ...
Martinis' Graduate Work Demonstrating Macroscopic Quantum Effects
John Martinis' work in quantum computing can be traced back to a pivotal moment early in his career, which set the stage for significant contributions to the field that have propelled quantum computing from theory to tangible research and application.
At the end of his thesis time, Martinis found inspiration at a conference where Richard Feynman discussed the potential of using quantum mechanics for computation—essentially building a quantum computer. The ideas presented at the conference were groundbreaking and planted the seed for Martinis's lifelong pursuit of making quantum computing a reality.
Following Feynman's talk, others in the field, like Peter Shor, began to delve into more specific aspects of quantum computation, including the development of algorithms capable of solving real-world problems using quantum mechanics. Shor’s factoring algorithm emerged about five years later and opened new avenues for quantum computer applications, which Martinis saw as the most fascinating fundamental question—melding quantum mechanics with computational processes.
The research Martinis undertook during his graduate studies played a pivotal role in encouraging a global research effort to build superconducting quantum computers. This effort has since evolved into a substantial field characterized by extensive publications an ...
Connection Between Martinis' Experiments and Quantum Computing Rise
John Martinis' work in superconducting circuitry during his graduate studies laid the foundation for the design and fabrication of superconducting qubits, which are essential for the development of quantum computers.
Martinis discusses his initial fascination with building quantum systems and how his role as an experimentalist propelled him to invent various devices critical for the functioning of quantum computers. He highlights the collective effort that has advanced the field over the years.
His early experiments with quantum tunneling in electrical circuits indicated the utility of Josephson junctions. These junctions are fundamental to creating qubits, wherein a metal wire combined with a Josephson junction behaves like an inductor, and another wire behaves as a capacitor, allowing the system to oscillate and form a qubit. This setup shows quantum mechanical behavior at low temperatures due to superconductivity.
Martinis was involved in the 2019 Google quantum supremacy experiment, employing a 53-qubit system to perform a mathematical algorithm far more efficiently than a classical computer could. This milestone demonstrated the significant capabilities of quantum computing.
Martinis' Contributions to Superconducting Qubit-Based Quantum Computers
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