By KRISTEN COYNE
Animation credit: Stephen Bilenky
It's the time of year when we celebrate perfect pairs, matches made in heaven, two attracted opposites melding into one romantic couple.
It turns out that some of the most intriguing duos aren’t human, but scientific. The realms of classical and quantum physics are full of terrific twosomes: pairs that can’t exist without each other, pairs that are bound together, pairs that follow one another, are attracted to each other, or that can even be two things — or in two places — at once!
Without further ado, here is our choice for the best pairs in physics.
6. North & south
Whether in electromagnets or permanent magnets, poles almost always come in pairs: There’s a north and a south to every magnet, which is why they’re called dipole magnets. Particles that are magnetic monopoles, theorized by physicist Paul Dirac decades ago, were created in a lab several years ago. No partner for them, thank you very much: They prefer the footloose, fancy-free lifestyle.
5. Electricity & magnetism
Electricity creates magnetism, magnetism creates electricity: The duo is truly the power couple of the universe. Of the four fundamental forces, electromagnetism has the biggest impact on our day-to-day lives, from enabling the gadgets, cars and appliances we use to holding atoms and molecules together.
4. Qubits, part I: Xs & Os & 1s
Today's computers rely on transistors to process "bits" of information in the form of binary 0s or 1s. But the quantum computers of the future will feature qubits (pronounced “Q-bits”), which can be in both the 0 and 1 states at the same time. Called a quantum superposition, this involves a mix of the two possible spin states of a molecule, with a spectrum of almost infinite possibilities between the two. Read more.
3. Qubits, part II: Entangled particles
When it comes to qubits and love, it’s complicated. They are known for their long-distance relationships, interacting with each other from afar using their magnetic fields. Perhaps a reference to the lovebirds’ ambivalence, this phenomenon is known as “entanglement.” In fact, in tomorrow’s quantum computer, large numbers of entangled qubits would perform in perfect unison. Unfortunately, magnetic disturbances can rock the boat in these relationships, resulting in some bad breakups (euphemistically referred to as "decoherence" by physicists). Read more.
2. Star-crossed quarks
Talk about co-dependent. Quarks, the fundamental building blocks of particles, just can’t stand to be alone. And any jealous killjoys trying to split these devoted pairs, beware: The force that holds them together gets stronger the more you pull them apart. So if, like warring Montagues and Capulets, some disapproving party should try to tear asunder these star-crossed quarks, it will soon find itself uncomfortably outnumbered. If enough energy is applied to separate the duo, that energy instantaneously results in not just one, but now two pair of quarks! (E =mc2!)
1. Cooper pairs
Most relationships have their ups and downs, their stresses and strains, their phases of friction. Electrons moving through a conventional conductor are no different, bumping into obstacles left and right, straying off the straight and narrow, getting hot under the collar. In superconductors, however, we find the most fortunate of lovers, matches made in science heaven. At sufficiently frosty temperatures, they bundle up into Cooper pairs that sashay right through the superconductor’s crystal lattice while all obstacles fall away, overpowered by true love. A quantum cupid called a phonon, is a positively charged wave that forms behind a moving electron, playing matchmaker by drawing a second, love-struck electron into the picture to form the pair. Read more.