IamA Quantum Computer Guy AMA!

Will quantum computers allow PUBG to run at a steady frame rate?

Probably not. They'll most likely be cloud based, so probably not responsive enough on those time scales.

I know there's a subreddit for that that I'll look up later, but how would you describe Quantum Computing to a five-year-old?

A computer is something that takes an input (like some button press), processes that input, and then gives you an output (like Mario jumping on a Goomba).

The processing is a mathematical problem that the computer has to solve. It does it by breaking the problem down into a whole bunch of very small problems: like the Lego of mathematics.

Some problems are easier to build out of these basic building blocks than others, and so there is a difference in how fast the computer can solve them.

Quantum computers use different building blocks to normal computers. They are like Lego Technic instead of Duplo. So they'll be able to solve problems that normal computers will struggle with.

ELI5 Lego Technic, Lego Duplo and their differences

There is a lot more subtlety to Technic. Pieces are smaller and there and there are more ways to connect them. Duplo is just sticking big blocks together. If you want to build anything more complex than a tower, you'll have to build it much bigger with Duplo than with technic.

The two systems are compatible though. So since Duplo is cheaper to build big things with, a Hybrid approach will probably be more efficient in many case.

All these things are also true for quantum computers and normal computers.

Do people actually call you Quantum Jim?

My fellow quantum people don’t, because they are quantum too. Normal people also don’t, because it would be weird.

How do you think quantum computing will effect cyber security or infrastructure security in the future? I’m sure there’s both Pros and Cons.

The downfall of current public key cryposystems will certainly be a significant effect. But there is definitely a lot of good research being done on how to replace them.

There is also quantum key distribution, which is already a commercial product.

Other than completely breaking everyone's favourite cryptography, though, I'm not sure what other threats are posed. Most weakness in security are with the humans at either end, after all.

What is the most common misconception you've heard regarding quantum computing?

The biggest I think is that people seem to think that even the inputs and outputs of quantum computers will be weird and quantum. They are just computers, and like any computer we will we feed them with our inane questions and need to receive understandable answers. It is only during the processing that the quantum magic happens.

So in a few years time, you may well be using packages that call on quantum functions, and never even realize it is happening. Quantum computing won't just be limited to people with PhDs.

How do you feel about this quantum computing comic?

SMBC is great. Scott Aaronson knows what he is talking about. So it is probably the best lesson that can be conveyed in comic form. But it is just a comic.

What would you say would be the most beneficial future use of quantum computing for humanity?

Performing calculations with quantum systems is something that quantum computers will do really well. This should be beneficial for anything whose design would benefit from a better understanding at the molecular or atomic level, like materials, chemicals and medicines.

How, exactly?

Quantum computers are will themselves be a large and complicated quantum thing. Just the kind of thing that is difficult to simulate. So it won't be too hard to hack them into pretending they are other quantum things that we want to study.

I misread the title of this as "I Made A Quantum Computer Gay". Then I realized I couldn't read, but it made me think-- can you make a quantum computer gay? Or is that more of an AI thing?

If Microsoft succeeds in building a topological quantum computer, it would be full of homeomorphisms. I think that’s about as close as I can get you.

Do you expect quantum CPUs to become compact enough to replace current CPUs in electronic devices, or do you think they'll remain too restrictive to be used anywhere outside of a room hotter than a few millikelvins (but really useful in that context)?

Current CPUs will always be needed, to handle inputs and outputs at the very least. So they'll always be around. And quantum processors, as you say, will likely always need extremely low temperatures. So quantum computing looks set to remain a cloud based endeavour.

Can you please explain why current CPUs will be needed to handle inputs and outputs? Is this due to the way quantum CPUs are designed?

Processing the input signals from a keyboard, and do basic number crunching on data sets are tasks that normal computers are great at. It would be hideously expensive to get quantum computers to do those tasks instead.

Also, quantum computers need to be fed signals via lasers, microwave pulses, etc to tell them what to do. Those will all be created by conventional technology. So you'll always need to write your quantum programs and get them compiled down to pulse sequences by normal computers.

If the tech can get sufficiently small and work at norm mark temps, would you expect a quantum card, similar to a graphics card? Something to use for small on site quantum activities?

Since a lot of computing is going on the cloud anyway, I don't see that there will be a lot of focus on trying to get quantum processors into peoples homes.

How does the actual coding compare to with conventional computers? Do instructions need to be shaped in a special way that takes advantage of the quantum-mechanical mechanisms underlying the architecture, or can you basically just write a standard program in e.g. a C-like language?

Coding a quantum computer is currently done at the machine level. So it's all manipulating bits (or qubits). If you want to have ints and addition, for example, you'll have to build them for yourself.

To construct these programs and send them to quantum computers, you'll need to use a standard computer. So your coding will mostly be in a standard language. Current SDKs typically use Python.

This program I wrote, creating a quantum superposition of emoticons, is intended as a simple 'hello world' like quantum prorgram. By checking out other examples in the same repo, you will hopefully begin to learn the advantages of quantum programming.

Edit: Since this has ended up as the most highly voted question on what quantum code looks like, I think I'd better add a snippet. Here's a very simple example of writing the bit string 00101 in a register of qubits and then reading it out.

q = QuantumRegister(5) # initialize array of 5 qubits
c = ClassicalRegister(5) # initial array of 5 standard bits
program = QuantumCircuit(q, c) # initialize quantum program

# qubits initialized in 0 state, so nothing needs to be done for q[0], q[1] or q[3]
# for the rest we apply a NOT
program.x(qr[2]) 
program.x(qr[4])
program.x(qr[5])

# extract a bit value for each qubit and write the results into the array b
for j in range(5):
    program.measure(q[j], c[j])

This is written using the QISKit SDK. The program is a python object which can be submitted to a real device using their API.

Not sure if this is a great place to ask. Or if it's insulting your intelligence, but I understand observing a particle causes the wave function to collapse, essentially making the particle a particle.

But why does observing something mean, what makes something observed?

One of the great mysteries at the heart of quantum mechanics certainly doesn't insult my intelligence ;)

This is the measurement problem which many have tried to address in different ways.

But from the perspective of quantum computing, it's just the thing that makes the qubit give us a result that our monkey brains can understand.

Just to add that a common misconception is that a consciousness is required to collapse the wavefunction. That's not true.

I'd argue that a good description of an object being observed, from the state point of view, is simply information about this object being emitted/extracted out of it (and out of the quantum scale into the macroscopic world). Whether there's a human/animal/(incoherent) atom/nothing receiving that information isn't important.

^ This quantum cake is true

After reading up on Grover's algorithm regarding O(√N) evaluations of inputs to a black box problem using quantum computers, as opposed to O(N) with classic computation, it feels like probability is broken and nothing makes sense. Am I missing something? What is your opinion?

it feels like probability is broken and nothing makes sense

It's not broken, it's just generalized to complex numbers! Scott Aaronson has some lecture notes on this you might be interested in.

This isn't the only way to think about what's happening in a quantum computer. In the end it is just linear algebra: multiplying lots of matrices together. But sometimes we can come up with better visualizations for specific cases. Like the Bloch sphere for single qubits.

What is love?

Baby don’t hurt me.

Are you afraid you will leap across time like Quantum leap, or end up as a computer program like in Tron?

I’m more afraid that I will not get to do either of those awesome things.

Are quantum computers something that will eventually become part of everyday computers, like a PCI-E expansion card, or will they remain cloud based? Would they even have applications in home computing?

I think they may indeed have home applications. Everyone has something that needs to perform some optimization algorithm now and again, and quantum computers can be very good at these.

Even so, I think they'll always be cloud based. Especially since even normal computing is migrating to the cloud these days.

It all depends on which architecture for quantum computing wins. But most will require the processor to be kept at near absolute zero temperatures. Unless your computer has liquid Helium cooling, that just isn't feasible to have at home.

Hi, more of a personal question: What would be the best way to get into quantum computing research at a professional level? I am totally fascinated by this topic, but after 1,5 years of searching I got the impression, that the European involvement in this area is quiet sparse.. (For the record: already M. SC. In Materials Sciences from Germany with specializations in atomic interaction simulations using DFT-Methods.) Thanks in advance. You guys rock!!

The traditional route is a Physics degree followed by a PhD. Maths and CS degrees are also good. I think there are experimental groups for which material science will also get you into a PhD program, but I can't give you any concrete pointers.

Europe may not have as much involvement as the US, but it is still quite strong. Especially with the newly launched EU flagship. So things should get stronger still.

As for non-traditional routes, you can start playing with the quantum SDKs (like QISKit) and other projects like OpenFermion. They should help build up skills that could land a job in a few years. But that depends on how the field develops.

I have an Astrophysics bachelor degree. Was thinking of going for masters in physics later. Would this path allow me to be involved in quantum computing or will not having masters in math or something hinder the path?

Physics is still the main route in to QC, though maths and CS degrees are good too. A physics masters is a good way to get into a PhD in the field, which is the traditional first step.

How long until we see a Quantum Computer AI vs Traditional Computer AI chess match?

That could use machine learning, which people might try to implement as soon as they can. I can see someone trying that for a bit of press coverage in 5 years or so. Whether it is a very convincing demonstration, however, is another matter.

Until then, there's Quantum Chess.

Did you ever hear the Tragedy of Darth Plagueis the Wise?

Isn't that the guy who could prevent Schroedinger's cat from dying?

I've read that when quantum computing becomes a broader reality that encryption as we know it will no longer function.

1. Do you think that's overstated?
2. How will the way we think about computers change?

Public key cryptography will require a significant overhaul. But once post-quantum crypto is in place, I would imagine that there would be little difference from an end-user perspective.

It might be like the millennium bug: lot's of work done behind the scenes to ensure that its all trivial for the public.

What is the biggest hurdle in development at the moment?

Also do you have any papers to read about quantom computers and prediction of protein structures?

The biggest hurdle is that qubits are affected by noise, which basically means any kind of interaction that we don't want to happen. If you initialize your qubit in a certain state, noise will completely mess it up in a tiny fraction of a second.

Also, our operations are not perfect. Whenever we do anything, it introduces a bit of extra noise. So after a sufficiently long program, everything just decays to nonsense.

This means we have to make everything much cleaner so we can sustain interestingly long programs, as well as implement quantum error correction which will make everything cleaner still.

How/why does noise affect the qubits?

Noise essentially just causes the qubits to drift away from the state they are supposed to be in. So if you set your qubit to be 0, there's always some probably that noise will come and turn it into a 1.

Can it run Crysis?

Battleships is the most complex game I've managed to run.

Can you mine Bitcoin with those Quantum Computers and if so how fast would it be?

Current devices are not big and clean enough to do any significant bitcoin mining. Once they are, crypto currencies would likely have adapted to be quantum resistant with post quantum crypto.

Have you guys achieved time travel even on a small scale?

Probably the closest I can give you is an experiment regarding indefinite causal order, in which past and future don't really make sense.

could you explain what indefinite causal order is?

Wibbly wobbly timey wimey ;)

The video I linked to will explain it better than I could, though probably still not in a way that makes a huge lot of sense.

I gotta know ... Is quantum computing and programming as cool as I think it is?

It is almost absolute zero. You can't get much cooler than that.

Is the CPU chip a different design on a quantum computer?

The architecture of a CPU is very different, although with similarities. They are based on qubits instead of bits, for one thing. Also, only reversible gates are used (so you need a Toffoli instead of an AND for addition, for example). There are also gates, like the Hadamard, that have no equivalent with bits.

Chip design also varies a lot between different ways of building a qubit. IBM and Google have quite different designs, even though both use superconductors to make qubits. Approaches based on trapped ions are extremely different, and the same is true for other approaches like spin qubits and photons too.

Not only am I sad that I missed this, but disappointed that questions were mostly satire.

If you're still doing this AMA, I'd love to hear from you. Feel free to answer all, any or none of these questions.

1. If quantum computers have the ability to simulate molecular structures, does this present an opportunity for material sciences to make substantial advances that pushes QC and traditional computing further?
2. Machine learning seeks to solve optimization problems. If quantum computers are exceptionally good at optimization, would QC eventually be the platform to run the computation side of things for ML/AI?
3. We're still at the very first stages of QC. Is there a consensus on whether or not we can write standard libraries/languages that are as intuitive to use as traditional programming in the future?

Thanks for taking the time to do the AMA. Sorry it wasn't better utilized.

I'm still at it!

1. I think this, as well as chemical and drug design, will be one of the most important uses for quantum computing. Of course, current materials scientists are very good at working within the possibilities given by standard computers. So they are getting on with that rather than giving us a big list of problems to solve. But once they get their hands on QC, I'm sure they'll make great use. And if that leads to less noisy and more efficient QC, that would be great.

2. There are indeed efforts to combine ML with QC. It's early days, but it is a big research effort.

3. That is certainly an aim. There is already a major library being built for quantum chemistry: OpenFermion.

I work in IT and I constantly hear lay people talking about how quantum computers are the computers of the future. What do you think about this statement?

From what I understand, quantum computers are designed for specialty calculations, and not "general OS usage".

Quantum computers will be part of the computing landscape of the future, but they will indeed be used for only the kinds of problem that normal computers can't tackle.

Normal computers are far too awesome to be replaced. And a quantum computer that could run Microsoft Office would need to be orders of magnitude larger and more expensive than a normal computer. So a hybrid approach with quantum cloud services will be the way to go.

I think the question everyone really wants to know is what will this do for gaming?

Seriously though, what kind of work is quantum CPUs be more efficient for versus conventional CPUs?? Which industries would/could be most effected by this technology? Are they going to put quantum CPUs into smartphones?

what kind of work is quantum CPUs be more efficient for versus conventional CPUs??

We have a big list of applications with a proven speedup for quantum computers. The one I think is most important is to do accurate and large scale simulations at the atomic level, which will be very useful for industries based on developing materials, chemicals or medicine. I'm sure that there will be a huge injection of new insights once devices are actually up and running.

Are they going to put quantum CPUs into smartphones?

Smartphones are getting bigger and more expensive as time goes on. But I don't think they'll get that big and expensive. It will certainly be accessible via the cloud on smartphones, as quantum devices already are now.

Are you familiar with the Navier Stokes equations for flow? They're highly non linear and analytical solutions to the equations don't exist. We have to resort to modelling techniques (computational fluid dynamics, finite element, finite volume, etc.,) to solve the Navier Stokes equations. This takes a long time! Will quantum computing slash solve times?

I can't say I'd heard of a method, and I can't see anything obviously applicable in the algorithm zoo. So probably it is too hard to find a nice, clean method with with an easily provable speedup (not surprising perhaps, since these aren't the sorts of terms we associate with Navier-Stokes!). Perhaps when good powerful quantum devices exist, some quick and dirty methods might be found.

Is there a way to tinker with quantum programming for the average person? Or is it still just a thing for PhDs?

Would be cool to be able to write little programs with it like how pretty much anyone can do with regular programming languages right now.

Is there a way to tinker with quantum programming for the average person?

Absolutely. IBM has a GUI interface to construct programs for some of their devices. They also have the QISKit SDK to do things with Python. This has lots of examples, including my superposition of emoticons.

Other companies also have similar efforts, like Rigetti and Alibaba.

What are the potential dangers of Quantum computing?

Will it lead to rogue AI like Skynet?

The dangers of quantum computers are pretty much the same as those of any other computer. You probably don't need quantum processors to build a Skynet.

One exception is that security in current crytography is based on problems that are too hard for computers to solve. Once we get quantum computers, current crypto will be useless. That could be dangerous if post-quantum crypto is not already in place.

But the same would also be true for normal computers if someone managed to bust out a useful proof of P=NP.

Will there be or is there any cross over between AI and quantum computing?

There is a lot of research into blending machine learning and quantum computing. Stick the two magical black boxes together and something is sure to happen!

Why does my brain feel like I am on hallucinogens when I read about and try to understand the nitty gritty of the quantum world?

Don't tell the government that we are providing legal highs, you'll probably get us banned!

Is "cat state" not the most awesome technical jargon in all of geekdom?

It’s best when contained in bras.

Are quantum computers capable of all tasks that classical computers can perform? Like playing games maybe?

Yes, they can do everything. Just in a much larger and more expensive way.

They certainly can play games. I and others have even made some!

https://medium.com/@decodoku/the-history-of-games-for-quantum-computers-a1de98859b5a

Will quantum computing ever allow for a stable Microsoft Office programme?!

They will take Microsoft Office to unimaginable levels of bloat and instability.

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That become a lot more common once they start solving problems that normal computers cannot. That will probably take 10 years at least, but if all goes well it could be less. I'm not sure how long until they are truly commonplace, though.

Programmer here. Can you post some quantum programming code that might make some sense to me, but also demonstrate what’s different about it?

The easiest answer for me to give is to point you to this Jupyter notebook I made. It has a simple task that flags up an important difference between classical and quantum variables. It also guides you through writing the quantum program yourself with an interactive tutorial.

Other examples are also available on the QISKit tutorial.

But this isn’t really a great reply for an AMA, because it would be better to have something shorter and sweeter. So I’ll try to revisit this later.

Can you do trigonometric function calculations on a quantum computer? I've seen adders ect but what about this?

You can do anything! Any normal program compiled down to reversible gates (like the Toffoli) can be ported directly to a quantum computer.

The ProjectQ quantum SDK we’re talking about implementing trigonometric functions at one point, but I don’t know if they have yet.

As for doing them faster than in normal computers, I don’t know of any method that’s been found for that.

Over the years each time I see some new promising breakthrough in computing, it seems to stall when it comes time to actually produce a product because there just aren't enough people who understand it well enough. I see that happening with AI right now. Is that a concern for quantum computing too?

Devices are currently too small and noisy to make a concrete product. So there's a few years to go before we get a shortage of expertise. Some in the community (like IBM, Rigetti and Alibaba) are trying to address this by getting their devices on the cloud and trying to engage new users (that's what my Hello Quantum project is about, in fact). If this effort is successful, we should be well positioned to take advantage when truly useful hardware is around.

Since general population is always like 20 years behind military; isn't it safe to assume the technology is actually alot further than is publicly known at this point?

The military have put a lot of money into civilian development of quantum tech. So I'm not sure they have anything behind the scenes.

I have read that quantum computer chips are being made (small one qubit chips). When could we expect larger?

There are already larger devices. IBM have 5 and 16 qubit chips on the cloud, and 20 and 50 qubit chips that are not publicly accessible. A startup called Rigetti has a 19 qubit device on the cloud and Alibaba has 11. Google is claiming a device as big as 72 qubits. They even have a fancy logo. But there are no results on that yet.

So they certainly are getting ever bigger.

I’m currently transferring to Berkeley as a physics major and am interested in getting into this field.

How would you recommend I do so??

Attending the quantum computing meetups hosted by your friendly neighbourhood quantum computing company would be a great thing to do for anyone in the Bay Area.

In your opinion, what are the odds were living in a computer simulation?

It would be a very big computation. I’m not sure why anyone would bother.

Which country has the fastest general purpose or commercialized Q-computer?

The US has the most devices on the cloud (in fact, IBM alone takes the crown for this). The US also has the biggest device (Google’s 72 qubits, though there’s no data on how well it works).

I think this most likely means that the US has the best device, though it is hard to determine exactly how to rank different devices at the moment.

Is my cat dead or isn't it?

If it doesn't seem to eat its food and never gives you any affection, it could well still be alive.

Do you know whats 1+1?

Since the operations for qubits are based on the group Z_2, I'll have to say 1+1=0.

Do you use instruction sets based on normal processors that are then adjusted for quantum computer processors?

There is a lot of influence from traditional information theory, but the instruction set is also very influenced by what can be done with the quantum systems.

The instruction set is basically those from reversible computing (like the NOT and Toffoli), with some extra quantum ones (like the Hadamard).

What is the optimal temperature for quantum computers to operate normally?

Zero Kelvin would be best. Other than that, as close as you can get.

This isn't necessity true for all possible implementations. For photonic quantum computers, where the information is carried and processed by photons, temperature is less important than detector efficiency. But some approaches to increasing detector efficiency require superconductors at very low temp. So you'll again need to pt everything in a fancy fridge.

I have read that Quantum computers will make virtually all current encryption methods totally useless. How realistic is this in your opinion?

Once large scale fault-tolerant quantum computers are built, they will the widely used public key crypto systems. Their security is based in the assumption that certain problems are too hard for computers, and those are the kinds of problems that quantum computers will be great at.

Even so, it will be a while until those kinds of devices exist (a decade at least) and post-quantum crytpo is in development.

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How to do cryptography when fully-fledged quantum computers are around is still a very active topic of research, and crypto-currencies will need to look at what solutions are found. Methods based on hash functions seem to be the most likely.

If you want to see an example of a paper that discusses these kinds of issues, check out this.

Which of the DiVinzenco criteria are the hardest ones to achieve, any why? I had to learn them for a module but never really had a practical insight.

The criteria for initialization, universal gates and readout are things that a given physical implementation will either provide or it will not. So we only go for ones that allow these things.

The criteria for low noise and scalability are not independent. Scaling up means introducing more noise channels, which then need to be suppressed. It is the combination of these two things that are the most challenging.

So to program a quantum machine, what are the steps? Do you have an example that isn’t something like solving some polynomial equation? I mean, this code compiles and runs on a conventional von-Neumann architecture:

Int x; Void main() { For (x=0;x<10:x++) ....

}

What are the mechanics to even create an algorithm and load it into the machine?

Programs are currently written at the machine code level. So even the concepts of addition, integers and loops in your snippet are pretty high level.

So for a simpler example, consider writing the bit string 00101 in a register of qubits and then reading it out.

q = QuantumRegister(5) # initialize array of 5 qubits
c = ClassicalRegister(5) # initial array of 5 standard bits
program = QuantumCircuit(q, c) # initialize quantum program

# qubits initialized in 0 state, so nothing needs to be done for q[0], q[1] or q[3]
# for the rest we apply a NOT
program.x(qr[2]) 
program.x(qr[4])
program.x(qr[5])

# extract a bit value for each qubit and write the results into the array b
for j in range(5):
    program.measure(q[j], c[j])

This is written using the QISKit SDK. The program is a python object which can be submitted to a real device using their API.

I made a 'Hello World' type program based on similar principles here.

Is it true the computers are still pretty crap at being used for actual research?

I'd say the opposite. The only thing they are currently good at is being used for research. The relevant research area being 'how good is this prototype quantum computer, and how can I make it better'.

They are also good at doing proof-of-principle stuff. Things that we are pretty certain about what result we'll get, but it's nice to see a quantum computer good enough to actually do it.

But as a tool for helping with other areas of research, they are still not up to much.

What would you recommend as the best way to invest (financially) into quantum computing now?

There are multiple articles currently in contention. Probably best not to bet on any specific one. Software is pretty platform independent, though, so perhaps a quantum firmware or software startup like QCtrl or Zapata.

But I am not a financey type person, so what do I know.

Will we ever have personal quantum computers?

That’s not likely, due to the cooling and shielding required. But you will have personal access via the cloud.

Who do you think will be first to practically deploy quantum computers and for what purpose?

Also, is it too late to invest in cryptocurrencies now, since quantum computing advances at such fast pace, heard it could make cryptocurrencies obsolete?

Who do you think will be first to practically deploy quantum computers and for what purpose?

There are already devices on the cloud that can be deployed for purposes such as doing experiments, or making simple versions of Battleships. But they are probably not a the kind of purposes you are interested in.

As for doing something that a normal computer cannot, Google are the ones most obsessed with achieving this. They aim to implement a proof-of-principle task (though not a useful one) within the next few years. Though Alibaba are making things harder on them by pushing the limits of what normal computers can do. (see here).

To do something actually useful, we might have to wait a decade or more until full fault-tolerant quantum computers are realized. But there is a big effort currently to find useful applications for the smaller and noiser quantum processors of the near term. Machine learning is a big possibility.

Also, is it too late to invest in cryptocurrencies now, since quantum computing advances at such fast pace, heard it could make cryptocurrencies obsolete?

I'm no expert on crytocurrencies, but I know you'd need a fault-tolerant quantum computer to break them. That's a decade away at least. Should be enough time to implement post-quantum crypto.

Are you swiss? (I am) What do you think Switzerland is going to be capable of in terms of quantum computing in the near/far future?(including the scientifics themselves) And how did you get there? Is it easy? Do you think it is "a worthy carrer path"?

I’ve been in Switzerland a good few years, but I’m originally from Britain.

Switzerland currently is currently quite good for quantum technology. The NCCR QSIT is the big government sponsored alliance (that I’m part of). We have some internationally competitive academic groups and companies in quantum computing and quantum cryptography. And IBMs quantum efforts also have a major outpost here.

I got here through the ‘old-fashioned’ route of a physics degree followed by a quantum computing PhD. But there are more accessible ways to get engaged these days. You could start with my Hello Quantum project.

As for the worthiness, it certainly will be a good career path in a few years things keep going at their current momentum. And if they don’t, I think it is closely related enough to other fields to be a good transferable skill.