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**What is Quantum Computing : **Quantum computing is computing using quantum-mechanical phenomena, such as superposition and entanglement. A quantum computer is a device that performs quantum computing.

They are different from binary digital electronic computers based on transistors. Whereas common digital computing requires that the data be encoded into binary digits (bits),

each of which is always in one of two definite states (0 or 1), quantum computation uses quantum bits, which can be in superpositions of states.

A quantum Turing machine is a theoretical model of such a computer, and is also known as the universal quantum computer. The field of quantum computing was initiated by the work of Paul Benioff (de) and Yuri Manin in 1980, Richard Feynman in 1982, and David Deutsch in 1985. A quantum computer with spins as quantum bits was also formulated for use as a quantum spacetime in 1968. What is Quantum Computer of work in Bitcoin.

## Quantum Computer Work in Bitcoin

**Bitcoin** is a digital currency and payment system based on classical cryptographic

technologies which works without a central administrator such as in traditional currencies. It

has long been questioned what the impact of quantum computing would be on Bitcoin, and

cryptocurrencies in general. Here, we analyse three primary directions that quantum

computers might have an impact in: mining, security, and forks. We find that in the nearterm

the impact of quantum computers appear to be rather small for all three directions. The

impact of quantum computers would require considerably larger number of qubits and

breakthroughs in quantum algorithms to reverse existing hash functions.

Mining Bitcoin would not be any better on a Quantum Computer. SHA-256, the algorithm used to mine Bitcoin, is a one way function. That means that you can pre-compute all the possibilities without running it, which what gives a quantum computer it’s power.

There are two main flavors of encryption at play in Bitcoin: What is Quantum Computer of work in Bitcoin

**1) Hashes** – Bitcoin uses SHA-256 and RIPEMD as hashing algorithms. This generates new blocks, hides an address from the public key, and allows some checksums.

**2) ECC** – This is the public/private key pair that lets you sign and prove you own your Bitcoin.

## About Quantum Security

ECC is vulnerable to a quantum attack, but you’d need the public key. Since the public key is protected by the hashing algorithms, which are thought to be quantum resistant, simply using change addresses and always emptying all inputs in a transaction sufficiently protects your coins.

You are only at risk if you don’t use this default behavior, which has been part of wallets for years now.

What is Quantum Computer of work in Bitcoin

## Mining System & Algirothms

**Mining :**

One of the technologies that Bitcoin is based on is the SHA-256, a cryptographic hashing

function which turns arbitrary input data into a 256 bit string (the “hash”). This is a one-way

function, so that it is easy to find the hash from an input but not the other way around.

Bitcoin mining consists of the search problem of finding an input (the “nonce”) combined

with information of the most recent block that generates a hash that is less than a target value

T, the maximum number that is acceptable to be considered a valid Bitcoin hash. The target “What is Quantum Computer of work in Bitcoin”

value is continually being readjusted such that the average time between blocks is 10 minutes

(at the time of writing the target is approximately T = 8.9x 10^{11}

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, much smaller than If it were possible to find a quantum algorithm to invert SHA-256

efficiently, then we could indeed mine Bitcoin easily. However, the value of Bitcoin comes

from the difficulty of finding such solutions, which gives it “proof of work”. Currently it is

believed that there is no efficient algorithm, classical or quantum, which can invert SHA-256.

Hence the only way is a brute force search, which classically means trying different inputs

until a satisfactory solution is found.

Quantum mechanically, we have Grover search, which seems to be a perfect solution to this

kind of problem, and has a quadratic quantum speedup. Let us see how well this strategy

works when comparing it to mining with a classical computer. Classically, the success

probability of mining a block with guesses is given by , where”r” is the hash rate (the

number of guesses made per second), and “t” is the time in seconds. For a quantum miner running Grover’s algorithm the success probability is

“rq” is the

number of Grover iterations per second, which we can call the “quantum hash rate”.

Now there is a different dynamic between the classical and quantum miner because Bitcoin is

designed to find a new block on average every 10 minutes (=600 seconds), and hence the

nature of the search problem changes in this time. In order for the Grover procedure to give a

high success probability, a quantum miner should run their algorithm for a time “t” before the

problem changes, and then make a measurement. Meanwhile, the classical miner has in this

time been trying as many nonces as possible. So the quantum miner is hoping that none of

the classical miners have found a solution yet during the Grover evolution. Since the interval

between blocks follows an exponential distribution, the probability that the block is still

mineable is given by

Assuming a constant cost of running a quantum computer for a

given amount of time, the profitability of quantum Bitcoin mining is then

where R is the reward (currently equal to the price of 12.5 Bitcoins plus transaction fees) andC

is the cost of running the quantum computer.

**What is Quantum Computer of work in Bitcoin**