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Blind Quantum Computing | QuTech Academy


Another great application of the quantum internet is that it enables secure access
to quantum computers in the cloud. So what does that mean? You can imagine, that just like how classical
computers were once rare and extremely expensive, early quantum computers are likely to be rare
and extremely expensive. So let’s imagine that quantum computers
are available and you want to use them from the comfort of your own home
or from the comfort of your own office. So, you buy some time on this quantum computer
in the cloud to perform your favourite calculation; and quantum computers promise to perform quite a few
calculation much faster than the classical computer. For example, quantum computers
are extremely good at factoring numbers. Now you might imagine that you want to use
the big quantum computer far away… ..to factor a number; and to do that, you actually send
a message over the classical internet saying “can you please factor this number for me?” For example, you might say, “Please factor 15”; and the quantum computer would send
a message back saying “15 is 5 times 3”. Let’s imagine however, that you actually want
to perform computations on sensitive data. For example, quantum computers are thought
to be very good at simulating molecules and performing calculations in chemistry. So you might imagine that maybe you want
to perform a computation involving a molecule that is proprietary or under investigation; or maybe, you want to use the big quantum computer
to perform a computation that involves your own DNA. Possibly, you would be somewhat more hesitant
to actually tell the quantum computer what your DNA is, in order to use its computing power. How can quantum solve this? Secure quantum computation in the cloud
solves this problem. And to achieve this, we need a quantum internet. Of course, if you needed a quantum computer at home, in order to access
the big quantum computer in the cloud, if you want to think historically,
the quantum mainframe far away, that would defeat the purpose; you already have a quantum computer at home,
so why not use it yourself? So what you really want is that you can have a cheap,
tiny quantum computer, a quantum terminal at home, which is an extremely simple quantum device; and you can use this simple quantum device
to talk to the big quantum mainframe far away. But in order to do this securely,
you want to send qubits to that big mainframe. So you can imagine that you only have
a tiny quantum terminal, which can only prepare and measure single qubits, and you’re going to use the quantum internet to send qubits that encode the secure computation
to the quantum mainframe far away. Then the big quantum mainframe is going
to perform the quantum computation for you and it’s going to return you messages from which you can learn the answer. It turns out that sophisticated protocols exist
that allow you to use the quantum computer without revealing your input data, like your DNA and even without revealing
what you actually want to compute. So the quantum computer will not know
whether you’re trying to factor a number, or whether you are trying to perform
a computation on some piece of DNA. This is known as secure delegated quantum
computing, or blind quantum computing; and it requires a quantum internet to transmit
qubits from the quantum terminal to the quantum mainframe in the cloud.

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