Microsoft Leaps into the Quantum Computing Race with Both Feet
Today's Majorana 1 Announcement Marks a Watershed Achievement for Microsoft and the Quantum Computing Industry
February 19, 2024.
Microsoft was founded by Bill Gates and Paul Allen in 1975, well before computing was a common offering. In November of 1980 they signed the first MS-DOS license with IBM, again well before PC’s were prevalent, but that contract was responsible for many billions of dollars in revenues in the following decades. It was a prescient act that suggests they had a keen vision of where the PC market might go, establishing Microsoft’s reputation as a market leader and trendsetter. This market leadership position has served the Company exceptionally well and today their market capitalization exceeds $3 trillion, making it the 3rd most valuable company on the planet. Microsoft’s ability to see into the technology future has remained with Microsoft (MSFT or the Company) many decades later, and today’s Majorana 1 announcement not only continues that tradition but marks their bold and exciting direct entry into the rapidly evolving Quantum Computing market.
In early 2022 I wrote a post about cloud-based quantum computing access and noted three providers in the space (Amazon, Microsoft and QC Ware) which were offering access to systems from six Quantum Computing providers. Microsoft’s role, at the time, of providing access to systems from three providers, made them seem like an early but minor player in the quantum field. I re-looked at Microsoft’s quantum efforts this past November and was impressed with their progress and dedication and wrote a post highlighting their quantum efforts at the time, which you can see here. I was fortunate enough to be invited to MSFT’s Quantum Summit last week at their Redmond, Washington headquarters, where they provided access to many of the key leaders of their quantum program, allowed access to their substantial quantum lab, and showcased their latest quantum efforts. I was considerably impressed with the continued progress. And as Mitra Azizirad, the President, COO and CVP Growth, Innovation, and Strategy, Strategic Missions and Technologies (who’s purview includes MSFT’s quantum efforts) told us, she has been at MSFT for 34 years and has seen many important advances and launches, but this Majorana 1 announcement is one of the most significant achievements she has witnessed during her long tenure with the Company.
The first part of this post, in Quantum Leap spirit, will be crafted for non-scientists, with no math and only minimal technical details. Given the bleeding-edge nature of the achievements, and the fact that Microsoft has created an entirely new form of matter, this will be difficult, but the news is so significant that I’m hoping to provide details that can excite readers of all levels. In the second half, for those curious or interested in a deeper dive, I’ll do my best to describe some of the more technical details, and finally, at the end, I’ll include some links to even more technical details.
Part I: For Non-Scientists
What is Majorana 1 and Why Was I So Impressed?
Today, as you can read here, Microsoft introduced Majorana 1 (pronounced my-oh-rana), the world’s first quantum chip driven by a new architecture that will power quantum computers capable of solving meaningful and practical problems that are difficult or impossible for traditional computers or existing AI to solve. Their timeline for this ultimate achievement is years, not decades.
For those of you familiar with Quantum Computing (QC), you may know that there are several different ways that companies create QCs, with some interesting tradeoffs among different types of cores (better known as qubits). There are electron, atomic and photonic qubits, each with varying pros and cons, but all suffering from “noise” which degrades the qubits rapidly, severely restricting the results current QCs can produce.
There are three key features of Microsoft’s new topological qubits that make them exciting new entrants in the rapidly advancing QC realm:
Their topological structure makes them more resilient to outside disturbances, or “noise”.
Microsoft has created a novel new way to implement QC instructions (known as “gates”), which uses measurement instead of rotations; and
These topological qubits have been designed for scaling, with 1 million readily fitting on one chip, which is smaller than a typical watch face.
Let’s drill down a bit on each of these features.
1. What is “Topological?”
Microsoft has opted to create qubits from a novel new construct, creating something called “topological” qubits. The “topo” portion of the name takes its meaning from the Greek for “place” or “location” and signifies the fact that these qubits store their information in the “place” or way the qubits are braided with each other, as opposed to all the other qubit modalities that store their information in the actual electrons, atoms or photons. To help you visualize this, imagine a mobius
strip, with a twist in it, such as in the photo below:
The strip on the left is untwisted, while the strip on the right has a twist. It’s possible to stretch and compress the strips without impacting whether there is or isn’t a twist. The only way to remove (or add) a twist is to physically cut or break the strip, and then reattach the ends, which takes considerable energy to do. This is analogous to topological qubits which, because of their physical structure, are significantly less vulnerable to disruptive system noise, which degrades all other forms of qubits. This relative resilience to noise is a core feature of topological qubits.
2. What Do You Mean Gates are Created by Measurement Not Rotation?
The way that topological qubits encode their information is a complex and novel configuration which leverages superconducting wires (which is why the cores need to be placed in dilution refrigerators and chilled to nearly absolute zero). The short story is that this novel construct contains electrons placed into a special state along a wire, with features at the ends known as quantum dots. When there are an “even” number of electrons in the wire, it has a different profile than when there are an “odd” number. When Microsoft engineers send a microwave signal to the quantum dots, the way it bounces back can distinguish between this even/odd differential in a highly reliable way. So, they get highly accurate measurement readings and do not need to do qubit rotations (more on this in Part II), which is a challenging feature of competing qubit modalities.
3. What about the special scaling features?
Currently, all superconducting QCs require operation in a dilution refrigerator at exceedingly cold temperatures, and it is especially challenging getting control signals in and out of the extreme cold. This is complicated by the fact that each superconducting qubit, needs its own control wires, and as the numbers of qubits increase, management of these wires and the data flow is particularly challenging. Atomic and photonic qubits each have their own scaling challenges. However, the construct of the topological qubits does not require a control wire for each qubit, and it efficiently manages the interface between the ultracold qubits and the room temperature control signals via a Cryo-CMOS set of controls embedded in the Majorana 1. Each qubit is microscopic and the Majorana 1 footprint is designed to eventually hold 1,000,000 qubits in its core, which is the small football stadium shaped rectangle in the center of the photo below, with the entire chip fitting on one dilution refrigerator:
That’s All Theoretical, But Does it Actually Work?
The short answer is, sort-of. Topological states of matter were theorized about 100 years ago by Italian physicist Ettore Majorana, whom the Majorana 1 is named after. He postulated the existence of a special particle, that was its own antiparticle, and which would have special properties. However, until 2012, such a particle was never observed, and it wasn’t until very recently that Microsoft was able to create and control Majoranas. Today, Microsoft took this one step further and announced the utilization of these Majoranas to create a topological qubit. This was a crucial milestone in the march toward utilizing these Majoranas to create a quantum supercomputer. Microsoft is working toward creating a device with 1,000,000 physical topological qubits, which would allow for 1,000 or more logical qubits.
So “yes” Microsoft has proven it can create highly accurate and functioning qubits out of Majoranas, and that these qubits will have strong protection from the noise that has plagued nearly all other forms of qubits. They have also presented a measurement-based mechanism to create actual gates. And, they have shown that they can very efficiently create logical qubits from physical qubits through a number of important partnerships (i.e., with Quantinuum and Atom Computing). So, while they have not yet shown a working topological quantum computer, they have shown their ability to produce all of the necessary components for creating one.
OK, When Will They Have a Working Topological Quantum Computer?
Of course, I asked this question, but the quantum team at Microsoft was hesitant to provide a specific answer because they are navigating unchartered waters. Topological qubits are very new, and the engineering requirements for scaling these to 1,000,000 qubits is quite challenging. That said, they have publicly stated a timeframe of years as opposed to decades. More specifically, the Defense Advanced Research Projects Agency (DARPA) has selected Microsoft for their Underexplored Systems for Utility-Scale Quantum Computing (US2QC) aimed at building a functional, scalable quantum computer by 2033, and I would expect Microsoft to achieve and announce intermediate milestones between now and then.
Key Takeaway: Microsoft already has one of the most robust internal quantum programs, with its own quantum programming language (Q#), one of the broadest cloud-based access portals (Quantum Azure, with eight different quantum computing platforms available), deep access to HPC (high performance computing) and AI resources (Copilot) which are crucial for integrating with quantum computing, important collaborations which have led to industry leading numbers of logical qubits (with Atom Computing and Quantinuum), and now their own novel form of topological Quantum Computer that has tremendous promise for scalability and accuracy. Today’s Majorana 1 announcement marks a watershed achievement for Microsoft and the Quantum Computing industry.
Part II: A Slightly Deeper Technical Dive
If you don’t want to dive a bit deeper into the technical details, please skip ahead to the “To Learn More” section, which includes links to some videos that are non-technical but provide some excellent visualization, otherwise, please read on.
The technical details of how Microsoft uses topoconductors to create and use topological qubits is quite complex. Rather than attempting to explain all the technical specifications, the following section is intended to provide a very high-level orientation so the reader can better appreciate how quantum computations may ultimately be performed on this system.
Topological Qubits and Gates
Microsoft has published a concrete device roadmap for creating fault-tolerant quantum computing architecture based on noise-resilient, topologically protected Majorana-based qubits, showcased in a paper release earlier today, which you can find here.
Topological qubits, like those being developed by Microsoft, utilize Majorana zero modes (MZMs), which are special quantum states that can exist in certain materials under very specific conditions:
They exist at zero energy, hence the “zero mode” part of the name;
They behave as their own antiparticles; and
They can be thought of as “half” of an electron
They are created using a combination of semiconducting nanowires, superconductors, and magnetic fields to create conditions where MZMs can exist at the ends of the nanowires. The quantum information is stored in the collective state of pairs of these MZM’s and the non-local storage is a key to the topological protection. The graphic below shows how MZM’s are created:
The graphic above depicts a nanowire of a semiconductor, (indium arsenide in MSFT’s case), that has strong spin-orbit coupling and places it in contact with an s-wave superconductor (MSFT uses aluminum), in the presence of an external magnetic field B. The nanowire device experiences a topological nontrivial phase with exponentially decaying Majorana bound states at both ends.
Graphic: R. M. Lutchyn, J. D. Sau, S. Das Sarma, Nature 556 74, 2018
The following shows how Microsoft uses this to form a qubit:
The blue and red strip in the center of the bottom rendering denotes the nanowire that was depicted in the prior graphic. The graphic below depicts two adjoining qubits and represents how a microwave signal is directed at the qubit with the nature of the resultant reflection revealing if there are an odd or even number of electrons in the wire, which translates into the 0 or 1 states.
Measurement, which also serves at gate functions, is reasonably straightforward and accurate, as shown below:
The initial configuration of the Majorana 1 contains eight H-shaped qubits in a tetron array as depicted below:
And the graphic below isolates one of the qubits and describes how measurements, or gates, are executed.
Zooming in on one of the “H” configurations which represents one qubit, performing a measurement on two adjacent arms on the qubit, such as quantum dots 2 and 4 in the image to the left, is an X-gate, and performing the measurement on two ends of a single arm of the “H”, such as quantum dots 3 and 4 in the image to the right, is a Z-gate. Once these two gates can be created, all of the Clifford gates can thereby be derived from combinations of these two gates. For example, a Y-gate can be created as follows:
And a Hadamard gate can be created through a sequence of Z-X-CNOT-X gates. While the non-Clifford gates are more complex, Microsoft is confident it can also create those gates.
Scaling Up
Microsoft’s readout technique for performing gate operations enables a fundamentally different approach to quantum computing in which measurements are used to perform calculations.
Each qubit described above, has an area of approximately 15 square microns, so it is possible to fit millions of qubits on a single wafer (that stadium shaped portion in the middle of the first graphic in this post). The gate operations, or measurements, are a bit complex but quite fast and the physical operations can be executed on a microsecond time scale
Traditional Quantum Computers rotate quantum states through precise angles, requiring complex analog control signals customized for each qubit and each operation. This complicates quantum error correction (QEC), much relies on the same sensitive operations to detect and correct errors. Microsoft’s approach performs error correction via simple digital pulses that connect and disconnect quantum dots form the nanowires. This digital control makes it practical to manage the large numbers of qubits needed for real-world applications and overcomes one of the main challenges facing current superconducting systems.
To Learn More:
A non-technical video overview with some great graphics and commentary from key players on Microsoft’s quantum team can be found on YouTube here.
A fireside chat with Chetan Nayak, a Technical Fellow at Microsoft and key developer of Majorana 1, can be found here.
A peer reviewed paper entitled “Interferometric Single-Shot Parity Measurement in InAs-Al Hybrid Devices” with additional technical details can be accessed here (may be behind a paywall).
And a detailed “Roadmap to fault tolerant quantum computation using topological qubit arrays” can be found here.
References:
Non-cited graphics courtesy of Microsoft.
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