Strengths and Weaknesses of Quantum Computing Zahid Hussain MS150200612, Virtual University of Pakistan Zahidhussain334@gmail.com Asma Talib ms150401131 studentvu6@gmail.com Abstract— Computers have evolved very much from last half century. The modern day computers are very small, fast, powerful and energy efficient. But this growth has a limit. Now scientists are working on a completely new kind of computer based on the Quantum physics rules. These computers are called quantum computers. The Quantum computers can solve many problems which are not solvable by the current classical computer systems. The large scale production of the Quantum computers will start soon, which will totally change the computers and this, will affect every field. Keywords— Quantum Computers, Qubit, Strengths and Weaknesses, Computation, I. INTRODUCTION Quantum computational complexity is an exciting new area that touches upon the foundations of both theoretical computer science and quantum physics. The computational power of quantum Turing machines (QTMs) has been explored by several researchers and many researchers and companies are working on it currently. Early work done by Deutsch and Jozsa showed how to utilize some inherently quantum mechanical features of QTMs. Their results and the later research results by Berthiaume and Brassard established the existence of oracles under which there exists some computational problems that QTMs can solve in polynomial time with certainty, whereas if we require a classical probabilistic Turing machine to produce the correct answer with certainty, then it must take exponential time on some inputs. Quantum computer works differently from the traditional computers. The traditional computers can work on and compute only one transaction at a time. On the other hand the quantum computers can work on and perform multiple transactions at the same time which increase their speed more than traditional computers. The fund amental building block of a quantum computer is Qubit as shown in the diagram. Figure: 1 Classical Bit Vs Qubit. An ordinary bit can compute or store 0 or 1 but a Qubit can work and operate in between the values of 0 and 1. Figure: 2 Shows Difference between digital bit and Qubit Qubits are made up of two things first is the controlled particles and second one is the means of control.