Phase & Interference

Who doesn’t know (and love) the Flash??

Unlike the last two weeks’ niche, bald headliners, this week’s centerpiece is one of the most well known comic book characters of all time, and one of my personal favorites: the Flash. Whether it’s Jay Garrick or Barry Allen or Wally West behind the mask, the scarlet speedster is a staple of the superhero conversation. He’s literally the reason that super speed is included in the ‘which power would you have’ debate. (Such a blessing to have something besides super strength and flight by the way.)

I won’t spend this issue getting into the pedantry of the Flash origin story because the CW has already told that tale in the most compelling and interesting way possible. Seriously go watch the first three seasons of the CW Flash, you will NOT regret it. No, I want to talk about the Flash in the context of his seemingly simple, yet insanely versatile power, because it selfishly fulfills some of the physics discussion for this week.

To understand the Flash and his unrealistically convenient version of super speed, you have to understand the “Speed Force”. That is, the cosmic plot armor energy source that exists behind the lightning that gave Barry (we’ll just standardize to my favorite iteration) his powers. The pedants in the room complain about how moving at any speed near what our speedster does will result in every dust particle in the air colliding with him and shredding him to pieces. The comics’ answer to that is “That’s cute, but Speed Force.” The Speed Force is literally the in-universe plot armor specifically granted to speedsters in Flash mythos.

Beyond the Speed Force, the Flash is just so cool because of how creatively he stretches his powers. Not only does he “phase” (different connotation) through objects by vibrating his every atom, but he can also throw the speed force lightning that trails him as he runs. Oh, and time travel. One of the coolest, and relevant to this week’s simulation, is the Flash’s ability to make a speed clone of himself. But let’s get to the physics.

Waves, but not really

If you’ll recall, week one’s sim was not only locked behind a question about phase, but also had a phase dial option that did pretty much nothing for that simulation. That was me planting seeds for this week. So, what exactly is phase? Well, firstly, the specific concept at hand is “relative phase”, not global phase. What that means is that the “phase” characteristic will vary between amplitudes/states, whereas global overarchs. But “phase” itself can kinda be described like the direction of the state. That’s literally what the Bloch sphere shows—the amplitudes describe how far north or south your state points (either 0 or 1), whereas phase is indicated by the state’s angle along the equator. So with the combination of phase and amplitude, we get a location on the sphere that best represents the state at hand.

That was a lot of jargon. Let’s simplify by considering what phase could mean in the context of waves. When multiple waves propagate with their wavelengths lining up in certain ways, they can combine or cancel each other out: interference. So bringing that concept back to quantum, the relative phase tells us how “in sync” the two states are. That relative phase, the “sync”, is what controls interference.

Interference, in the case of quantum, adds those amplitudes just like in waves, but now the amplitudes are driving probability, like we discussed in week one. Now with the combination of both phase and amplitude, we have a more complete understanding of what matters to a superposed state.

Now’s a perfect time to check out this week’s simulation: Control the phase of Barry and his speed mirage, see where the two might end up!

PREDICT/before you run it

In week 1 the phase dial did nothing at all. Now the two routes are allowed to meet before anything is measured. What does that same dial do?

Still nothingSweeps him from one rod to the otherSends him to both rods at onceMakes the result random

Lock it in

SIM/both-paths

Both paths

Watch for the two dials. Turn them together and nothing happens — only the difference between them is real.

Press run

Bloch sphereFringe curveHide

PHASE = LONGITUDE · HEIGHT UNCHANGED

the state — phase is longitude, odds are height

▸What am I looking at?

One Flash reaches the accelerator and doesn't pick a route — he takes both, which is why two blurs leave the splitter. He's moving far too fast to see properly; what you're watching is the light he leaves behind.

Each dial delays one copy. That delay is phase. Turn both dials together and nothing happens at all — only the difference between them is real. A phase that everything shares is undetectable in principle, not merely hard to measure.

Where the routes meet, the two halves of him add together. In step they reinforce and he lands at one rod every time. Half a turn out of step they cancel — and he lands at the other rod every time. He is never destroyed. Cancelling here means arriving there.

Watch the sphere while you turn a dial: the arrow swings around without ever changing height, and height is what sets the odds. That is exactly why phase did nothing in week 1. Only when the routes recombine does the arrow tilt — longitude becomes latitude, and the phase you couldn't see turns into odds you can.

Copy A0°

Copy B0°

Difference that matters0°D0 100% · D1 0%

RunLoopWatch which route he takes

Reset

predicted D0 100.0%routes both open

Speedsters in Phase

The speed clone ability is explained with a big stretch of science — vibrating fast unleashes simultaneous possibilities of a speedster’s actions. It’s classic comic science fiction, but the way clones combine literally requires them to match frequencies. When their frequencies match, they’re in phase, and that’s when contact and/or recombination is possible.

There are two routes, two states. For the “interference” to occur, we have to watch their phase.

Where the comics fall short of the physics is the usual: the optimistic assumption that we can have our super-speed cake and eat it too. The speed clone makes us believe that interference allows us to take both paths and leave it at that, when in reality, the physics dictates that both paths might destructively interfere (cancel out) and you’re forced to arrive in one spot, often not the one you expected. Anyone else sense the stench of ‘false analogy’ in here?

The Long Awaited Character Analysis

As hopeful as he is, Barry Allen’s past is still littered with tragedy: his mother was murdered, and his father framed for the crime. To make matters more confusing, the perpetrator is Barry’s future arch nemesis, trying to ensure that tragedy forges his future (time shenanigans). That’s arguably one of the most compelling parts of Barry’s story: he’s the chosen one, not because of some arbitrary cosmic force, but because another man chose and wrote his future for him.

Flashpoint is one of the most infamous story lines, both in and out of the comics. Superheroes aren’t perfect, and Flashpoint answers the question: “What if the Flash was Selfish?” What would happen if, for once, a hero chose his own happiness? What would happen if Barry went back in time and saved his mother from the Reverse Flash?

This story, and the Flash, are so important to superhero culture, because they humanize our hero. In saving his mom, the entire timeline (in classic butterfly effect fashion) is blown up seemingly beyond repair. Barry is the only man aware of the two timelines, and so responsibility befalls him to bring the timeline back into phase. The story doesn’t ruin the Flash and marinate him in his failure; it uplifts him further because he has to make the sacrifice of “unfixing” his life.

The Flash reminds us that comic characters aren’t really supposed to be super-human. The best characters are those that toe this line between human and hero, those that make mistakes and choose to fix them. But we’re not perfect. How do we know we chose the right timeline?

Be sure to check back in next week for issue 04! Until then,

Happy Reading!