An Intro to Quantum Computing

In my last two articles, I talked about how Artificial Intelligence and Personalized Medicine have the ability to positively impact the healthcare industry. Another upcoming technology that could do the same thing is Quantum Computing.

Quantum Computing, Quantum Physics, Quantum Mechanics? Sounds futuristic.

Quantum Mechanics is really a branch of physics that classical mathematical equations can’t describe. In classical mechanics, objects are either at Point A or at Point B. However, shrink down to the scale of electrons or atoms and that’s when quantum mechanics come into play, objects can be at Point A and at Point B, at the same time! Take a look at the following quantum phenomena that govern sub-atomic particles:


A particle can be a particle and a wave at the same time, basically particles are thought to exist in every possible state (a single particle can be in different positions, have different energies or be moving at different speeds), all at the same time! Mathematically, superposition is represented as

|ψ> = α|0> + β|1>

where ψ (psi) represents the state of superposition and the 1 and 0 represent the qubits.

When we push the spin of an electron into a superposition of both possible states (spin up and spin down), the electron is said to have a simultaneous spin of both states. When measuring this qubit, we collapse the superposition and force it into one of these two possible states (50% chance of measuring either 1 or 0). In this case, we basically performed the equivalent of flipping a coin using the quantum laws that govern the sub-atomic world. As soon a qubit is measured, it has a certain chance of collapsing based on the probability of the qubit’s position in between the energy states. The mathematical way to represent this is

|α²| + |β²| = 1

where the absolute values of α² and β² represent probabilities.

Think about photons (particles of light). Through classical mechanics, we know that the three types of light: infrared, visible and ultraviolet are all electromagnetic waves. However, an experiment from 1923 showed that light scattered through by an electron beam, changed in color. The conclusion from this was that photons were colliding with electrons (particles of matter), proving that light particles can behave as both, a wave and a particle.

Quantum Tunneling

A particle can literally pass through barriers. Once again, thinking to classical physics, if a ball is not given enough velocity, it will not roll over a hill. However, at the quantum scale, objects exhibit wave-like properties so if a particle is rolling up a potential hill, the wave function (probability of detecting this certain particle on the other side of the hill) describing the particle could extend it to the other side of the hill.


Two particles, spatially separated by any distance, somehow affect each other. In classical mechanics, unless object A and object B physically meet, both objects are independent. At the quantum state, it is possible to prepare two particles in a single quantum state so when one is observed to spin upwards, the other one will almost always be observed to spin downwards.

Imagine this, a qubit α and a qubit β are entangled. If qubit α collapses to a state of 0, qubit β will almost always simultaneously collapse to a state of 1.

So What?

At this point, you might be thinking who cares, these phenomena happen at such small scale, they don’t affect anybody.

Think Again! On the web, you might have seen headlines like a quantum computer with 300 qubits can do more calculations simultaneously than there are atoms in the universe or the unveiling of Google’s recent 72 qubit processor. Now, you may think we have 72 qubits, just another 228 to perform a bunch of calculations but this assumption is way off.

Quantum Computing is becoming a popular technology and by using quantum computers to apply the quantum phenomena of sub-atomic particles to solve complex mathematical problems. How?

Classical Computers vs Quantum Computers

Classical computers transfer data through transistors, which are basically switches that allow electrical current to pass through them when on and don’t allow current to pass through when off. Having two states like this (on and off) is known as being “binary”. The value 1 is assigned to the on state and 0 is assigned to the off state (bits are either 1 or 0).

However, Quantum Computers aren’t binary so they have “qubits” to supply and communicate information throughout the computer system. Essentially, Quantum Computers change the state of a sub-atomic particle and uses this specific state to reflect a data value.

100 classical bits equals to 100 pieces of information while 100 functioning qubits could equal to 1,267,650,600,228,229,401, 496,703,205,376 pieces of information. This just shows how much more powerful quantum computers could be than today’s classical computers.

Quantum Phenomena in a Quantum Computer

IBM’s Quantum Computer

Superposition allows qubits to be coded with quantum information in states of 0 and 1, allowing a qubit to be in multiple locations at once. A complex system of qubits can multiple superposition states at once. Each qubit has two states, 0 and 1 so if you have X qubits, you’ll have 2^X possible states. Entanglement is also used as two qubits in the same quantum state are related in such a way that data from one qubit will provide information on the other qubit, and vice versa.

These Quantum Phenomena provide Quantum Computers with the ability to “optimize”, basically they can go through each possible solution or possibility of a problem at the same time and find the best way, effectively solving such problems in seconds or minutes, while classical computers would have to go through each possible solution one-by-one, taking years to solve large-scale problems.

Look at the following example, someone draws a circle on a random page of a random book in a library. Give this information to a classical computer and it would take years to find the page with the circle. For a Quantum Computer, the phenomena of superposition would allow a qubit to be in multiple places at once so it would look through each page in the library simultaneously and find the circle within seconds.


Qubits range in size from the size of an electron (2.82 x 10^-15 m) to a phosphorous atom (1.92 x 10^-10 m). Similar to the way transistors are used to implement bits, electron spins (magnetic fields in subatomic dimensions) are used to implement qubits. Instead of 0’s and 1’s, quantum computing uses the states of “spin up” and “spin down” with spin down being the lowest energy state.

Take a look at some of the different types of qubits being used today. Each type has a few individual properties such as:

  • State Longevity: how long can a quantum superposition state survive
  • Logic Success Rate: the highest reported functioning rate for operations regarding two qubits
  • Qubits Entangled: the number of qubits entangled that are able to perform two qubit operations

The Hurdle: Decoherence

Okay, so you know that Quantum Computers have this great potential to perform complex tasks in a short period of time, but there’s still one problem. When coding for a quantum algorithm, a three step process of activating qubits to reach all superposition states, apply a phase to each superposition state and then use methods of interference to cancel or add previous phases to optimize the correct solution. The key problem is that the more qubits present in a system, the higher the error rates. To have a functioning quantum computer, certain measures must be taken:

  • all qubits must be in a known state
  • entangle pairs of qubits
  • create a decoherent environment by calculating all possibilities of error and cooling down the system to as close to 0 Kelvin degrees (a temperature so cold that atoms essentially stop moving) as possible

Imagine a coin balanced on it’s rim as neutral (not heads, nor tails -> superposition state). Any small force applied on the coin will result in the coin falling on either heads or tails (0 or 1). This small force on the coin is similar to decoherence for a qubit; any interaction with the environment such as light, sound, heat, magnetic fields and measuring a qubit can lead to the elimination of quantum behavior in sub-atomic particles.

The result of decoherence is that quantum computational errors occur and lead to the loss of information. The key problem is that we are not able to read the processed data once quantum information processing has been disturbed. As previously mentioned, the time that qubits are able to survive their quantum state is known as coherence length or state longevity. Increasing coherence length is the key to having quantum computers compute mathematical problems faster than classical computers (achieving “quantum supremacy”, having Quantum Computers replace Classical Computers).

How do we do this? Quantum Error Correction (QEC). Copies of quantum information can’t be made due to the no-cloning theorem (a theory that states that copies of information can only be made with classical bits, not qubits in superposition state). Therefore, QEC is used by applying the phenomena of entanglement to detect and correct quantum computational errors while maintaining the quantum properties of a qubit.

Quantum Computing in Healthcare

Now that you have an understanding of what Quantum Computing is, take a look at how it will positively impact the healthcare industry.

Quantum Computing and Genome Sequencing

Genome sequencing is the process of determining the order of the four DNA bases [adenine (A), thymine (T), cytosine (C), guanine (G)] in our DNA. Today, genome sequencing involves taking the DNA apart into smaller parts and looking for certain biomarkers that are similar to mutations found in a reference genome. There are two key problems with this process: manual operation is required and the process is very long but not fully accurate.

The fact is genome sequencing requires a lot of computational power and storage as a person’s entire genetic information is being represented but classical computers normally don’t have such power.

A Quantum Computer, with much more computational power and storage, could go through each gene variant simultaneously and find the order of the DNA bases much quicker with better accuracy. This method would remove the needs of a manual operator and a reference genome.

The result of using a Quantum Computer to find specific biomarkers and disease related mutations with better accuracy would mean that patients would receive a proper diagnosis and recover.

Quantum Computing and Personalized Medicine

Genome sequencing ties into personalized medicine as by analyzing the genotypes and phenotypes expressed in a patient’s genome, individualized therapy plans could be created (click here to learn more about personalized medicine). Since it is becoming much easier for people to have their DNA sequenced (price drops from multi-millions to about $100), more people will get their DNA sequenced, creating a lot of data.

By using Quantum Computing to sift through all this data and tailor medical plans for each patient, patients will efficiently recover without the risk of having their health decline due to general treatments. As well, from a research perspective, creating a database of human genomes and using Quantum Computing to analyze this database could reveal unknown patterns about the way our DNA is “encoded” and further our understanding of certain mutations and their relationships with our genes.

Quantum Computing and Medication Discovery

Using the phenomena of superposition and entanglement, Quantum Computers can find all possible variants at the same time, giving them the ability to sift through large amounts of data efficiently and accurately.

One application of this property is the ability to simulate chemical interactions between molecules. Classical computers are unable to do this because the large amount of data would take years to sift through, as is seen by the average of 12 years it takes to determine, research and produce a new medication. Part of this process involves accounting for each possible combination of electron interactions (sharing, repelling or attracting between atoms). Classical computers go through the innumerable possibilities for a new medication one-by-one.

Quantum computers could efficiently and accurately go through each possibility of a molecule’s structure in an instant and simulate ionic and molecular compounds that are yet to be physically experimented with for healthcare purposes. With such computational power, quantum computers could revolutionize the way we look at pharmaceutics, healthcare and biochemistry.

Just imagine out of an endless amount of possibilities, being able to optimize the best possible solution and find cures to viruses and diseases that classical computers couldn’t. The solution for each patient to be cured of their respective disease in an instant. That’s Quantum Computing.

My Personal Note

Now, you can probably see that Quantum Computing has a massive potential to replace classical computers and through the use of Quantum Phenomena, we can solve complex mathematical problems instantly. In terms of Healthcare, the impact Quantum Computing could have is very significant as we could be looking at genome sequencing, personalized medicine and medication discovery much differently. These impacts are what awaits a future based on Quantum Computing.

Key Takeaways

  • Quantum Phenomena such as superposition, quantum tunneling and entanglement govern the sub-atomic world
  • Quantum Computers use Qubits instead of Bits to solve mathematical problems more accurately and efficiently than a classical computer
  • Quantum Computers heavily rely on superposition and entanglement
  • Decoherence is the key obstacle for Quantum Computers
  • Quantum Error Correction (QEC), using entanglement to detect and correct quantum computational errors may be the solution to decoherence
  • Quantum Computing will benefit the healthcare industry through fields like genome sequencing, personalized medicine and medication discovery

“Just as the 19th century was called the Machine Age and the 20th century the Information Age, the 21st century promises to go down in history as the Quantum Age.”

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