quantum

23 Articles

This Week In Security: The Geopolitical Kernel, Roundcube, And The Archive

October 25, 2024 by 12 Comments

Leading off the week is the controversy around the Linux kernel and an unexpected change in maintainership. The exact change was that over a dozen developers with ties to or employment by Russian entities were removed as maintainers. The unfortunate thing about this patch was that it was merged without any discussion or real explanation, other than being “due to various compliance requirements”. We eventually got more answers, that this was due to US sanctions against certain Russian businesses, and that the Linux Foundation lawyers gave guidance that:

If your company is on the U.S. OFAC SDN lists, subject to an OFAC sanctions program, or owned/controlled by a company on the list, our ability to collaborate with you will be subject to restrictions, and you cannot be in the MAINTAINERS file.

So that’s that. One might observe that it’s unfortunate that a single government has that much control over the kernel’s development process. There were some questions about why Russian entities were targeted and not sanctioned Chinese companies like Huawei. [Ted Ts’o] spoke to that, explaining that in the US there are exemptions and different rules for each country and business. This was all fairly standard compliance stuff, up until a very surprising statement from [James Bottomley], a very core Kernel maintainer:

We are hoping that this action alone will be sufficient to satisfy the US Treasury department in charge of sanctions and we won’t also have to remove any existing patches.

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This Week In Security: Quantum RSA Break, Out Of Scope, And Spoofing Packets

October 18, 2024 by 13 Comments

Depending on who you ask, the big news this week is that quantum computing researchers out of China have broken RSA. (Here’s the PDF of their paper.) And that’s true… sort of. There are multiple caveats, like the fact that this proof of concept is only factoring a 22-bit key. The minimum RSA size in use these days is 1024 bits. The other important note is that this wasn’t done on a general purpose quantum computer, but on a D-Wave quantum annealing machine.

First off, what is the difference between a general purpose and annealing quantum computer? Practically speaking, a quantum annealer can’t run Shor’s algorithm, the quantum algorithm that can factor large numbers into primes in a much shorter time than classical computers. While it’s pretty certain that this algorithm works from a mathematical perspective, it’s not at all clear that it will ever be possible to build effective quantum computers that can actually run it for the large numbers that are used in cryptography.

We’re going to vastly oversimplify the problem, and say that the challenge with general purpose quantum computing is that each q-bit is error prone, and the more q-bits a system has, the more errors it has. This error rate has proved to be a hard problem. The D-wave quantum annealing machine side-steps the issue by building a different sort of q-bits, that interact differently than in a general purpose quantum computer. The errors become much less of a problem, but you get a much less powerful primitive. And this is why annealing machines can’t run Shor’s algorithm.

The news this week is that researchers actually demonstrated a different technique on a D-wave machine that did actually factor an RSA key. From a research and engineering perspective, it is excellent work. But it doesn’t necessarily demonstrate the exponential speedup that would be required to break real-world RSA keys. To put it into perspective, you can literally crack a 22 bit RSA key by hand.

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Quantum Sensor Uses Synthetic Diamond

August 18, 2024 by 3 Comments

Diamonds are nearly perfect crystals, but not totally perfect. The defects in these crystals give the stones their characteristic colors. But one type of defect, the NV — nitrogen-vacancy — center, can hold a particular spin, and you can change that spin with the correct application of energy. [Asianometry] explains why this is important in the video below.

Interestingly, even at room temperature, an NV center stays stable for a long time. Even more importantly, you can measure the spin nondestructively by detecting light emissions from the center.

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Neopixels? Try Liquid Nitrogen To Color Shift Your LEDs Instead

November 11, 2023 by 23 Comments

If you’re like us, you’ve never spent a second thinking about what happens when you dunk an ordinary LED into liquid nitrogen. That’s too bad because as it turns out, the results are pretty interesting and actually give us a little bit of a look at the quantum world.

The LED fun that [Sebastian] over at Baltic Lab demonstrates in the video below starts with a bright yellow LED and a beaker full of liquid nitrogen. Lowering the powered LED into the nitrogen changes the color of the light from yellow to green, an effect that reverses as the LED is withdrawn and starts to warm up again. There’s no apparent damage to the LED either, although we suppose that repeated thermal cycles might be detrimental at some point. The color change is quite rapid, and seems to also result in a general increase in the LED’s intensity, although that could be an optical illusion; our eyes are most sensitive in the greenish wavelengths, after all.

So why does this happen? [Sebastian] goes into some detail about that, and this is where quantum physics comes into it. The color of an LED is a property of the bandgap of the semiconductor material. Bandgap is just the difference in energy between electrons in the valence band (the energy levels electrons end up at when excited) and the conduction band (the energy levels they start at.) There’s no bandgap in conductive materials — the two bands overlap — while insulators have a huge bandgap and semiconductors have a narrow gap. Bandgap is also dependent on temperature; it increases with decreasing temperature, with different amounts for different semiconductors, but not observably so over normal temperature ranges. But liquid nitrogen is cold enough for the shift to be dramatically visible.

We’d love to see the color shift associated with other cryogens, or see what happens with a blue LED. Want to try this but don’t have any liquid nitrogen? Make some yourself!

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Royal Navy Tests Quantum Navigation

June 7, 2023 by 33 Comments

GPS has changed the way we get around the globe. But if you command a warship, you must think about what you would do if an adversary destroyed or compromised your GPS system. The Royal Navy and Imperial College London think a quantum navigation system might be the answer.
Of course, Heisenberg says you can’t know your speed and position simultaneously. But at the real-world level, you can apparently get close enough. The quantum sensors in question are essentially accelerometers. Unlike conventional accelerometers, though, these devices use ultracold atoms to make very precise measurements using a laser optical ruler, which means they do not drift as rapidly as, say, the accelerometer in your phone. Navigating with accelerometers is well understood, but the issue is how often you have to correct your computed position with an actual reference due to drift and other error accumulation. You can see a Sky News report on the trial below. Continue reading “Royal Navy Tests Quantum Navigation” →

Quantum Inspired Algorithm Going Back To The Source

October 27, 2020 by 4 Comments

Recently, [Jabrils] set out to accomplish a difficult task: porting a quantum-inspired algorithm to run on a (simulated) quantum computer. Algorithms are often inspired by all sorts of natural phenomena. For example, a solution to the traveling salesman problem models ants and their pheromone trails. Another famous example is neural nets, which are inspired by the neurons in your brain. However, attempting to run a machine learning algorithm on your neurons, even with the assistance of pen and paper would be a nearly impossible exercise.

The quantum-inspired algorithm in question is known as the wavefunction collapse function. In a nutshell, you have a cube of voxels, a graph of nodes, or simply a grid of tiles as well as a list of detailed rules to determine the state of a node or tile. At the start of the algorithm, each node or point is considered in a state of superposition, which means it is considered to be in every possible state. Looking at the list of rules, the algorithm then begins to collapse the states. Unlike a quantum computer, states of superposition is not an intrinsic part of a classic computer, so this solving must be done iteratively. In order to reduce possible conflicts and contradictions later down the line, the nodes with the least entropy (the smallest number of possible states) are solved first. At first, random states are assigned, with the changes propagating through the system. This process is continued until the waveform is ultimately collapsed to a stable state or a contradiction is reached.

What’s interesting is that the ruleset doesn’t need to be coded, it can be inferred from an example. A classic use case of this algorithm is 2D pixel-art level design. By providing a small sample level, the algorithm churns and produces similar but wholly unique output. This makes it easy to provide thousands of unique and beautiful levels from an easy source image, however it comes at a price. Even a small level can take hours to fully collapse. In theory, a quantum computer should be able to do this much faster, since after all, it was the inspiration for this algorithm in the first place.

[Jabrils] spent weeks trying to get things running but ultimately didn’t succeed. However, his efforts give us a peek into the world of quantum computing and this amazing algorithm. We look forward to hearing more about this project from [Jabrils] who is continuing to work on it in his spare time. Maybe give it a shot yourself by learning the basics of quantum computing for yourself.

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Duality Of Light Explored By Revisiting The Double-Slit Experiment

October 18, 2020 by 41 Comments

We’ve all seen recreations of the famous double-slit experiment, which showed that light can behave both as a wave and as a particle. Or rather, it’s likely that what we’ve seen is the results of the double-slit experiment, that barcode-looking pattern of light and dark stripes, accompanied by some handwaving about classical versus quantum mechanics. But if you’ve got 20 minutes to invest, this video of the whole double-slit experiment cuts through the handwaving and opens your eyes to the quantum world.

For anyone unfamiliar with the double-slit experiment,  [Huygens Optics] actually doesn’t spend that much time explaining the background. Our explainer does a great job on the topic, but suffice it to say that when coherent light passes through two closely spaced, extremely fine openings, a characteristic pattern of alternating light and dark bands can be observed. On the one hand, this demonstrates the wave nature of light, just as waves on the ocean or sound waves interfere constructively and destructively. On the other hand, the varying intensity across the interference pattern suggests a particle nature to light.

To resolve this conundrum, [Huygens] jumps right into the experiment, which he claims can be done with simple, easily sourced equipment. This is belied a little by the fact that he used photolithography to create his slits, but it should still be possible to reproduce with slits made in more traditional ways. The most fascinating bit of this for us was the demonstration of single-photon self-interference using nothing but neutral density filters and a CCD camera. The explanation that follows of how it can be that a single photon can pass through both slits at the same time is one of the most approachable expositions on quantum mechanics we’ve ever heard.

[Huygens Optics] has done some really fascinating stuff lately, from variable profile mirrors to precision spirit levels. This one, though, really helped scratch our quantum itch.