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Quantum information theorists are shedding light on entanglement, one of the spooky mysteries of quantum mechanics

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theconversation.com – William Mark Stuckey, Professor of Physics, Elizabethtown College – 2024-07-30 07:45:00
Can the theory of relativity inform quantum mechanics?
koto_feja/E+ via Getty Images

William Mark Stuckey, Elizabethtown College

The year 2025 marks the 100th anniversary of the birth of quantum mechanics. In the century since the field’s inception, scientists and engineers have used quantum mechanics to create technologies such as lasers, MRI scanners and computer chips.

, researchers are looking toward building quantum computers and ways to securely transfer information using an entirely new sister field called quantum information science.

But despite creating all these breakthrough technologies, physicists and philosophers who study quantum mechanics still haven’t up with the answers to some big questions raised by the field’s . Given recent developments in quantum information science, researchers like me are using quantum information theory to explore new ways of thinking about these unanswered foundational questions. And one direction we’re looking into relates Albert Einstein’s relativity principle to the qubit.

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Quantum computers

Quantum information science focuses on building quantum computers based on the quantum โ€œbitโ€ of information, or qubit. The qubit is historically grounded in the discoveries of physicists Max Planck and Einstein. They instigated the development of quantum mechanics in 1900 and 1905, respectively, when they discovered that light exists in discrete, or โ€œquantum,โ€ bundles of energy.

These quanta of energy also come in small forms of matter, such as atoms and electrons, which make up everything in the universe. It is the odd properties of these tiny packets of matter and energy that are responsible for the computational advantages of the qubit.

A large machine with several layers of electronics.
Qubits could give quantum computers, such as IBM’s Q System One, a significant advantage over classical computers.
AP Photo/Ross D. Franklin

A computer based on a quantum bit rather than a classical bit could have a significant computing advantage. And that’s because a classical bit produces a binary response โ€“ either a 1 or a 0 โ€“ to only one query.

In contrast, the qubit produces a binary response to infinitely many queries using the property of quantum superposition. This property allows researchers to connect multiple qubits in what’s called a quantum entangled . Here, the entangled qubits act collectively in a way that arrays of classical bits cannot.

That means a quantum computer can do some calculations much faster than an ordinary computer. For example, one device reportedly used 76 entangled qubits to solve a sampling problem 100 trillion times faster than a classical computer.

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But the exact force or principle of nature responsible for this quantum entangled state that underlies quantum computing is a big unanswered question. A solution that my colleagues and I in quantum information theory have proposed has to do with Einstein’s relativity principle.

Quantum superposition and entanglement allow qubits to contain far more information than classical bits.

Quantum information theory

The relativity principle says that the laws of physics are the same for all observers, regardless of where they are in , how they’re oriented or how they’re moving relative to each other. My team showed how to use the relativity principle in conjunction with the principles of quantum information theory to account for quantum entangled particles.

Quantum information theorists like me think about quantum mechanics as a theory of information principles rather than a theory of forces. That’s very different than the typical approach to quantum physics, in which force and energy are important concepts for doing the calculations. In contrast, quantum information theorists don’t need to know what sort of physical force might be causing the mysterious behavior of entangled quantum particles.

That gives us an advantage for explaining quantum entanglement because, as physicist John Bell proved in 1964, any explanation for quantum entanglement in terms of forces requires what Einstein called โ€œspooky actions at a distance.โ€

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That’s because the measurement outcomes of the two entangled quantum particles are correlated โ€“ even if those measurements are done at the same time and the particles are physically separated by a vast distance. So, if a force is causing quantum entanglement, it would have to act faster than the speed of light. And a faster-than-light force violates Einstein’s theory of special relativity.

Quantum entanglement is important to quantum computing.

Many researchers are to find an explanation for quantum entanglement that doesn’t require spooky actions at a distance, like my team’s proposed solution.

Classical and quantum entanglement

In entanglement, you can know something about two particles collectively โ€“ call them particle 1 and particle 2 โ€“ so that when you measure particle 1, you immediately know something about particle 2.

Imagine you’re mailing two friends, whom physicists typically call Alice and Bob, each one glove from the same pair of gloves. When Alice her box and sees a left-hand glove, she’ll know immediately that when Bob opens the other box he will see the right-hand glove. Each box and glove combination produces one of two outcomes, either a right-hand glove or a left-hand glove. There’s only one possible measurement โ€“ opening the box โ€“ so Alice and Bob have entangled classical bits of information.

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But in quantum entanglement the situation involves entangled qubits, which behave very differently than classical bits.

Qubit behavior

Consider a property of electrons called spin. When you measure an electron’s spin using magnets that are oriented vertically, you always get a spin that’s up or down, nothing in between. That’s a binary measurement outcome, so this is a bit of information.

Two diagrams showing electrons passing through magnets. The top diagram shows one on top and one below the electrons' path. The electrons are either deflected up or down, as indicated by the split paths, after passing through the magnet. The bottom diagram shows two magnets, one on the left and one on the right of the electrons' path. The electrons are either deflected left or right, as indicated by the split paths, after passing through the magnet.
Two magnets oriented vertically can measure an electron’s vertical spin. After moving through the magnets, the electron is deflected either up or down. Similarly, two magnets oriented horizontally can measure an electron’s horizontal spin. After moving through the magnets, the electron is deflected either left or right.
Timothy McDevitt

If you turn the magnets on their sides to measure an electron’s spin horizontally, you always get a spin that’s left or right, nothing in between. The vertical and horizontal orientations of the magnets constitute two different measurements of this same bit. So, electron spin is a qubit โ€“ it produces a binary response to multiple measurements.

Quantum superposition

Now suppose you first measure an electron’s spin vertically and find it is up, then you measure its spin horizontally. When you stand straight up, you don’t move to your right or your left at all. So, if I measure how much you move side to side as you stand straight up, I’ll get zero.

That’s exactly what you might expect for the vertical spin up electrons. Since they have vertically oriented spin up, analogous to standing straight up, they should not have any spin left or right horizontally, analogous to moving side to side.

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Surprisingly, physicists have found that half of them are horizontally right and half are horizontally left. Now it doesn’t seem to make sense that a vertical spin up electron has left spin (-1) and right spin (+1) outcomes when measured horizontally, just as we expect no side-to-side movement when standing straight up.

But when you add up all the left (-1) and right (+1) spin outcomes you do get zero, as we expected in the horizontal direction when our spin state is vertical spin up. So, on average, it’s like no side-to-side or horizontal movement when we stand straight up.

This 50-50 ratio over the binary (+1 and -1) outcomes is what physicists are talking about when they say that a vertical spin up electron is in a quantum superposition of horizontal spins left and right.

Entanglement from the relativity principle

According to quantum information theory, all of quantum mechanics, to include its quantum entangled states, is based on the qubit with its quantum superposition.

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What my colleagues and I proposed is that this quantum superposition results from the relativity principle, which (again) states the laws of physics are the same for all observers with different orientations in space.

If the electron with a vertical spin in the up direction were to pass straight through the horizontal magnets as you might expect, it would have no spin horizontally. This would violate the relativity principle, which says the particle should have a spin regardless of whether it’s being measured in the horizontal or vertical direction.

Because an electron with a vertical spin in the up direction does have a spin when measured horizontally, quantum information theorists can say that the relativity principle is (ultimately) responsible for quantum entanglement.

And since there is no force used in this principle explanation, there are none of the โ€œspooky actions at a distanceโ€ that Einstein derided.

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With quantum entanglement’s technological implications for quantum computing firmly established, it’s nice to know that one big question about its origin may be answered with a highly regarded physics principle.The Conversation

William Mark Stuckey, Professor of Physics, Elizabethtown College

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The Conversation

Genetically modified varieties are coming out of the lab and into homes and gardens

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theconversation.com – James W. Satterlee, Postdoctoral Fellow in Plant Genetics, Cold Spring Harbor Laboratory – 2024-09-16 07:26:49

Not every rose has its thorn, thanks to gene editing.
James Satterlee, CC BY-SA

James W. Satterlee, Cold Spring Harbor Laboratory

As any avid gardener will tell you, plants with sharp thorns and prickles can you looking like you’ve had a -in with an angry cat. Wouldn’t it be nice to rid plants of their prickles entirely but keep the tasty fruits and beautiful flowers?

I’m a geneticist who, along with my colleagues, recently discovered the gene that accounts for prickliness across a variety of plants, roses, eggplants and even some species of grasses. Genetically tailored, smooth-stemmed plants may eventually arrive at a garden center near you.

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Acceleration of nature

Plants and other organisms evolve naturally over time. When random changes to their DNA, called mutations, enhance survival, they get passed on to offspring. For thousands of years, plant breeders have taken advantage of these variations to create high-yielding crop varieties.

In 1983, the first genetically modified organisms, or GMOs, appeared in agriculture. Golden rice, engineered to combat vitamin A deficiency, and pest-resistant corn are just a of examples of how genetic modification has been used to enhance crop plants.

Two recent developments have changed the landscape further. The advent of gene editing using a technique known as CRISPR has made it possible to modify plant traits more easily and quickly. If the genome of an organism were a book, CRISPR-based gene editing is akin to adding or removing a sentence here or there.

This tool, combined with the increasing ease with which scientists can sequence an organism’s complete collection of DNA โ€“ or genome โ€“ is rapidly accelerating the ability to predictably engineer an organism’s traits.

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By identifying a key gene that controls prickles in eggplants, our team was able to use gene editing to mutate the same gene in other prickly species, yielding smooth, prickle- plants. In addition to eggplants, we got rid of prickles in a desert-adapted wild plant species with edible raisin-like fruits.

Two sets of two photos. First set shows a cluster of prickly fruits on a plant and the harvest of those prickly fruits. Second set shows the same plant with fruits but without prickles and the harvest of those prickle-free fruits.
The desert raisin (Solanum cleistogamum) gets a makeover.
Blaine Fitzgerald, CC BY-SA

We also used a virus to silence the expression of a closely related gene in roses, yielding a rose without thorns.

In natural settings, prickles defend plants against grazing herbivores. But under cultivation, edited plants would be easier to handle โ€“ and after harvest, fruit would be reduced. It’s worth noting that prickle-free plants still retain other defenses, such as their chemical-laden epidermal hairs called trichomes that deter insect pests.

From glowing petunias to purple tomatoes

, DNA modification technologies are no longer confined to large-scale agribusiness โ€“ they are becoming available directly to consumers.

One approach is to mutate certain genes, like we did with our prickle-free plants. For example, scientists have created a mild-tasting but nutrient-dense mustard green by inactivating the genes responsible for bitterness. Silencing the genes that delay flowering in tomatoes has resulted in compact plants well suited to urban agriculture.

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Another modification approach is to permanently transfer genes from one species to another, using recombinant DNA technology to yield what scientists call a transgenic organism.

A photo taken in the dark shows a glowing petunia plant.
The firefly petunia is genetically engineered to glow in the dark.
Ceejayoz, CC BY-SA

At a recent party, I found myself crowded into a darkened bathroom to observe the faint glow of the host’s newly acquired firefly petunia, which contains the genes responsible for the ghost ear mushroom’s bioluminescent glow. Scientists have also modified a pothos houseplant with a gene from rabbits, which allows it to host air-filtering microbes that promote the of harmful volatile organic compounds, or VOCs.

A purple tomato is sliced open to reveal purple flesh inside.
The Norfolk purple tomato is colorful to the core.
Norfolk Healthy Produce, CC BY-SA

Consumers can also grow the purple tomato, genetically engineered to contain pigment-producing genes from the snapdragon plant, resulting in antioxidant-rich tomatoes with a dark purple hue.

Risks and rewards

The introduction of genetically modified plants into the consumer market brings with it both exciting opportunities and potential challenges.

With genetically edited plants in the hands of the public, there could be less oversight over what people do with them. For instance, there is a risk of environmental release, which could have unforeseen ecological consequences. Additionally, as the market for these plants expands, the quality of products may become more variable, necessitating new or more vigilant consumer protection laws. Companies could also apply patent rules limiting seed reuse, echoing some of the issues seen in the agricultural sector.

The future of plant genetic technology is bright โ€“ in some cases, quite literally. Bioluminescent golf courses, houseplants that emit tailored fragrances or flowers capable of changing their color in response to spray-based treatments are all theoretical possibilities. But as with any powerful technology, careful regulation and oversight will be crucial to ensuring these innovations benefit consumers while minimizing potential risks.The Conversation

James W. Satterlee, Postdoctoral Fellow in Plant Genetics, Cold Spring Harbor Laboratory

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Will your phone one day let you smell as well as see and hear whatโ€™s on the other end of a call?

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theconversation.com – Jian Liu, Assistant Professor of Electrical Engineering and Computer Science, of Tennessee – 2024-09-16 07:27:05

Phones that transmit odors seem like a great idea, but careful what you wish for!

Teo Mahatmana/iStock via Getty Images

Jian Liu, University of Tennessee

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Curious Kids is a for of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.


Is it possible to make a phone through which we can smell, like we can hear and see? โ€“ Muneeba K., age 10, Pakistan


Imagine this: You pick up your phone for a video call with a friend. Not only can you see their face and hear their voice, but you can also smell the cookies they just baked. It sounds like something out of a science fiction , but could it actually happen?

I’m a computer scientist who studies how machines sense the world.

What phones do now

When you listen to music or to someone on your phone, you can hear the sound through the built-in speakers. These speakers convert digital signals into physical vibrations using a tiny component called a diaphragm. Your ears sense those vibrations as sound waves.

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Your phone also has a screen that displays images and . The screen uses tiny dots known as pixels that consist of three primary colors: red, green and blue. By mixing these colors in different ways, your phone can show you everything from beautiful beach scenes to cute puppies.

Smelling with phones

Now how about the sense of smell? Smells are created by tiny particles called molecules that float through the and reach your nose. Your nose then sends signals to your brain, which identifies the smell.

So, could your phone send these smell molecules to you? Scientists are working on it. Think about how your phone screen works. It doesn’t have every color in the world stored inside it. Instead, it uses just three colors to create millions of different hues and shades.

How your sense of smell works.

Now imagine something similar for smells. Scientists are developing digital scent technology that uses a small number of different cartridges, each containing a specific scent. Just like how pixels mix three colors to create images, these scent cartridges could mix to create different smells.

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Just like images on your phone are made of digital codes that represent combinations of pixels, smells produced by a future phone could be created using digital codes. Each smell could have a specific recipe made up of different amounts of the ingredients in the cartridges.

When you receive a digital scent code, your phone could mix tiny amounts of the different scents from the cartridges to create the desired smell. This mix would then be released through a small vent on the phone, allowing you to smell it. With just a few cartridges, your phone could potentially create a huge variety of smells, much like how red, green and blue pixels can create countless colors.

Researchers and companies are already working on digital odor makers like this.

The challenges to making smell phones

Creating a phone that can produce smells involves several challenges. One is designing a system that can produce thousands of different smells using only a few cartridges. Another is how to control how strong a scent should be and how long a phone should emit it. And phones will also need to sense odors near them and convert those to digital codes so your friends’ phones can send smells to you.

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The cartridges should also be easy to refill, and the chemicals in them be safe to breathe. These hurdles make it a tricky but exciting area of research.

An odiferous future

Even though we’re not there yet, scientists and engineers are working hard to make smell phones a reality. Maybe one day you’ll be able to not only see and hear your friend’s birthday party over the phone, but also smell the candles they blew out!


Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the where you .

And since curiosity has no age limit โ€“ adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.The Conversation

Jian Liu, Assistant Professor of Electrical Engineering and Computer Science, University of Tennessee

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a double shot of US history

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theconversation.com – Kyle G. Volk, Professor of History, of Montana – 2024-09-16 07:28:46

a beer in Raceland, La.

Russell Lee for Farm Security Administration/WPA

Kyle G. Volk, University of Montana

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Text saying: Uncommon Courses, from The Conversation

Uncommon Courses is an occasional from U.S. highlighting unconventional approaches to teaching.

Title of course:

โ€œIntoxication Nation: Alcohol in American Historyโ€

What prompted the idea for the course?

I wanted to get about studying the past by learning about something that is very much a part of their own lives.

Alcohol โ€“ somewhat surprisingly to me at first โ€“ featured prominently in my own research on minority rights and U.S. democracy in the mid-19th century. As a result, I knew quite a bit about the temperance movement and conflicts over prohibition during that period. Designing this course allowed me to broaden my expertise.

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What does the course explore?

Prohibition is a must-do subject. Students expect it. But I several hundred years of history: from the 17th-century invention of rum โ€“ as a byproduct of sugar produced by enslaved people โ€“ to the rise of craft beer and craft spirits in the 21st century.

A faded poster with an illustration of a person about to smash a huge bottle of alcohol, and the message 'Close the saloons' at the top.

A temperance poster from the World War I era.

Office of Naval Records and Library via National Archives Catalog

Along the way, I’m thrilled when students get excited about details that allow them to taste a more complicated historical cocktail. For example, they learn why white women’s production of hard cider was crucial to the survival of colonial Virginia. The short answer: Potable was in short supply, alcoholic drinks were far healthier, and white โ€“ and their indentured and enslaved workforce โ€“ were busy raising tobacco. It fell to women to turn fruit into salvation.

Why is this course relevant now?

Alcohol remains a big and almost inescapable part of American society. But of late, Americans have been drinking differently โ€“ and thinking about drinking differently.

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Examples abound. Alcohol producers, we learn, now face competition from legalized weed. Drinking l evels rose during the COVID-19 pandemic, yet interest is declining among Gen Zers. The โ€œwine momโ€ culture that brought some mothers together now faces mounting criticism.

And, of course, there’s the never-ending debate about the health benefits and risks of alcohol. Of late, the risks seem to be dominating headlines.

What’s a critical lesson from the course?

Alcohol has been a highly controversial, central aspect of the American experience, shaping virtually all sectors of our society โ€“ political and constitutional, business and economic, social and cultural.

What materials does the course feature?

What will the course prepare students to do?

Like any history course, this one aims to develop student’s analytical, written, research and verbal skills. In lots of ways, the topic is just a tool to get students to grow their brains. But I also seek to grow students’ critical awareness of the place of alcohol in their own lives. The course has also informed students’ paths after graduation โ€“ including some who wound up working in the alcohol industry or recovery organizations.The Conversation

Kyle G. Volk, Professor of History, University of Montana

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