# Look At Quantum Computing Information Technology Essay

The study area that concentrates on the implementation of quantum theory principles for developing the computer technology is called Quantum computing. The main focus here is given to clarify the nature and character of energy and matter on the level of quantum. There is a lot of development in the quantum computing from the last billion-fold area in increasing the capacity of quantum computer in the similar way how the development from abacus to today’s super computer. Quantum computing can be understood by learning the quantum laws of physics by which so much of processing power is achieved and the capacity will be developed to several states and these will together helps in executing the tasks in terms of parallel attainable combinations. Generally quantum computing depends on quantum laws of physics because there are many advantages from the quantum physics atoms and nuclei properties which are definite, as the quantum physics laws and quantum computing are permitted by these properties to work mutually as quantum bits or simply as qubits, to be the processor or memory of a computer. The advantage of qubits is particular calculation are made faster exponentially when compared to the usual computers.

The computations on usual binary characters is not the base for qubits always, because by using the usual computers the information is encoded using the binary characters particularly into bits is encoded into ‘1’ or ‘0’ and also the calculations for only one set of number can only done at a time. But in case of the quantum computers information is encoded into a series of quantum mechanical states like electrons in spin direction or arrangement of photon polarization which can also be represented with ‘0’ or ‘1’, or can also be represented as superposition of many numbers which are not similar and sometimes represented as a number that express the state of qubits represented among ‘1’ or ‘0’ anywhere or may also represented as orientation of both.

## 2.1.1 Advantages of Quantum Computing:

The main advantage of quantum computing is it can execute any task very faster when compared to the classical computer, generally the atoms changes very faster in case of the traditional computing whereas in quantum computing it changes even more faster. But all the tasks can’t be done better by quantum computing when compared to traditional computer.

In quantum computing qubit is the conventional superposition state and so there is an advantage of exponential speedup which is resulted by handle number of calculations.

The other advantage of quantum computing is even classical algorithm calculations are also performed easily which is similar to the classical computer.

## 2.1.2 Disadvantages of Quantum Computing:

The main disadvantage of computing is the technology required to implement a quantum computer is not available at present. The reason for this is the consistent electron is damaged as soon as it is affected by its environment and that electron is very much essential for the functioning of quantum computers.

The research for this problem is still continuing the effort applied to identify a solution for this problem has no positive progress.

## 2.2 Quantum key distribution protocol (QKDP):

Quantum key distribution is a technology which depends on the quantum physics laws and this is used for the production and distribution of cipher keys that are secure into few unsecured channels. Here photon technology identifies the third parties or eavesdroppers who try for probable eavesdropping in the quantum channels, for this the technology uses quantum bit errors. If the information is encoded and sent randomly then the single photon produces the distributed keys that are secure and secret. The estimation of probabilistic character and state of photon are estimated by the help of these distributed secret keys. Quantum key distribution system has two channels called quantum channel and classical channel. Quantum channel is used in the quantum key distribution system for transmission of qubits or single photons along a transparent optical path. Whereas the classical channel is paired strongly with the quantum channel in order to gain timing requirements and this classical channel is also considered as the usual IP channel.

There is much variation between the quantum cryptography and traditional cryptography because of the reason that laws of physics are concentrated more in quantum cryptography. Particularly the data transmission and data saving in the quantum cryptosystem are done by using the laws of physics. For example, in a electric optical fiber, when the transmission of polarized photon is done then a secret key is created with help of optical fiber which can be considered as an secure channel. This secret key is generated in the form of a bits string that is random. These bit strings that are random are used in quantum cryptography in the same way like the secret keys are used in traditional cryptography. At present, many protocols for quantum key distribution are implemented, and these protocols are known as the B92 protocol, EPR protocol and two states protocol etc. The first implemented QKDP (Quantum key distribution protocol is called as BB84 protocol, this is designed by Gilles Brassard and Charles Bennet, this protocol is the most used protocol even now a days.

If we consider an example with two communication parties A and B, let A be the sender and B be the receiver and let the third party or eavesdropper be E. In this case of Quantum key distribution, the unconditional secure key should be distributed between A and B by noticing the existence of E. The security of QKDP is ensured differently with the help of quantum mechanics principles when it is regarded with the comparison to usual distributed key techniques which relies on the estimation of calculations that are yet to be verified. In usual techniques while the information is transferring the third parties cannot gain the knowledge of the data transferred because they don’t posses required resource to perform computations.

## 2.2.1 Advantages of Quantum key distribution protocol is:

The main advantage of QKDP is it allows the detection of eavesdropping because the error level will be comparatively more when the eavesdropper connects to the quantum channel than the error level that occurs naturally. Along with the detecting of eavesdropping, quantum mechanics laws will also allows the process of setting the error level between the intercepted data in dependence. Unrestricted security is provided by the QKD protocols and during this process isolation extension is permitted at the same time quantity of data is decreased considering the key that can be interrupted by the Eavesdroppers.

The other advantage of this protocols is the utilization of supreme key which is permitted by the additional encryption with the help of the traditional algorithms that are symmetric and known in the “quantum key distribution’s information theoretic security”. Therefore entire data security is increased by this QKDP.

## 2.2.2 Disadvantages of quantum key distribution protocol:

The considerable disadvantage of QKDP is very high price for business-oriented QKD systems.

Complete solution for the distribution of keys is not provided by the network release in the systems supported by the Quantum key distribution protocols.

Weak coherent pulses are used instead of the single photon pulses for decreasing the effectiveness of protocol. Conversely controlling this technology may be compressed in future if the usage of these coherent pulses is continued.

The transfer rate will be decreased immediately with the rise of channel length.

As the key rate decreases there will be a problem of photon registration results.

An error may occur by the photon during the data transmission due to the photon depolarization in quantum channel.

Practical realization is difficult particularly in quantum systems at d-level in QKD protocols.

## 2.3 QKD Introduction:

Quantum key distribution is a technique that uses the fundamental laws of quantum mechanics in order to achieve security key and also to ensure security. This QKD is also called as QKA that is the Quantum key Agreement. Generating a private key in more number between the two parties or among a public channel that is not secure is the main aim of QKD protocols. The single condition for the QKD protocols is the error rate must be less than the actual threshold then the information of the quantum will be communicated over a public channel. In order to enable secure communication between the authorized parties a resultant key is utilized, this is to establish a “conventional private key cryptosystem”.

The proposal of Quantum key distribution is developed first by Bennett and Brassard in the year 1984 and that protocol is called as BB84 protocol. The development of QKD has extended to the free space systems and optical fiber system. In the year 2000, G.L Morgan has reported the use of QKD in a 48 km distanced optical fiber network. This is developed in a better way in the year 2002 by the University of Geneva; this development is usage of QKD in the 67 km distanced of optical fiber network. This attempt was done successfully. In the year 2003, Guo’s group has developed a QKD in the 14.8 km special network of optical fiber, and this distance was expanded in a great range for the year 2004. Later it is also reported that in a 50 km optical fiber network. QKD can stay constant for six years. The Zeng’s group has demonstrated a quantum communication practically in a local area network using the TCP protocol. Japanese researchers have done many advanced researches and accomplished a single photon interference experiment for the quantum cryptographic system along 100km distance. This experiment is done using a balanced “gated-mode photon detector”. N.Gisen has developed solutions for the problems of chromatic dispersion using the constant fiber quantum channel along 30km distance for using the energy based entanglement based on the quantum key distribution.

A fiber optic QKD system is developed by using the optical fiber as a standard telecommunications and that QKD system is a short wavelength gigahertz clocked system which is useful for the quantum key distribution along a short distance metropolitan scale networks or metropolitan campus networks. Z.L.Yuan has achieved a quantum key distribution across a constant telecom fiber network of 122km distance. The photon that is entangled is directly distributed to the 7.8 km distanced receiver’s station particularly at night. In the year 2007, a QKD system was executed across an optic fiber network of 25km, this QKD system is a “reverse re-conciliated coherent-state continuous variable system. A free space system or a QKD system based on entanglement is established over 144km network. Later in the year 2008, an entangled QKD system is established over a links of two free space optical fibers, nearly 1,575 m is separated completely by these links. T. Honjo et al has experimented on the QKD system based on primary entanglement across a 100 km distanced optical fiber network in the year 2008 itself. These experiments of various researchers have continued for the year 2009 also and in the year 2009, a QKD system based on the entangled state is established between the source and the destination over a network of a distance of 300 km and even in if in more distanced networks.

All the above experiments of various researchers have proved that the usage of quantum cryptography and quantum communication is precise in real life applications. The fact is that earlier commercial quantum cryptographic device is offered for the application in real time. And so the QKD protocol is presented in the year 2004 along with the analysis of QKA protocol and its efficiency. In Quantum cryptography, most important and technical support is achieved by the quantum key distribution. QKD can be considered as the advanced tool for the cryptographers for making a secure key agreement using an un-trusted channel, which means QKD permits an channel that is un-trusted to make a secure key agreement. In quantum cryptography, the out is dependent on the input in using QKD and this is not possible in traditional cryptography. QKD is used build the systems using the designed security properties and so the additional cryptographic primitives like authentication are also existed in the system.

The additional primitives that are existed in quantum cryptography are quantum money, blind quantum computation, quantum coin tossing and quantum public key encryption; these primitives are designed by using the medium-to-large quantum computer. Many research groups have researched on the QKD systems and the implementations are done and considered as complex economically and so the usage of QKD will be high in the future security infrastructures.

In quantum key distribution systems there are three phases to establish a communication most securely. The three steps are as follows:

Key Agreement: In this phase the two parties that participate in the communication concurs a distributed private key which is secure.

Authentication: In this phase few authentication forms are used to avoid the attacks on key agreements mainly the “main-in-the-middle” attacks. For this a message is sent from the specific explicit party.

Key Usage: In this phase a secure key having the additional primitives or authentication is established using a cipher or a one-time pad for attaining encryption.

Quantum key distribution is just a part of the entire data security infrastructure which depends on the private key, this private key is concurred by the two parties that participates in the communication which is not based on the input of the protocol and also there are no computational assumptions for the security of private key to depend on. The authentication for the key agreement and the security in the infrastructure of public key for a long-term is achieved by using the public key cryptography and Quantum key distribution together as a combination. A private channel is required by the QKD for establishing authentication for the key. For example public key cryptography is not employed securely any longer by using the trusted courier of the key that is traditional over a private channel. Comparing the quantum key distribution outputs the sessions keys are more than the required amount of communication that is private. As the keys are distributed by the QKD over a private channel and the keys that are distributed are not dependent on each other, and this can be consider as an advantage in quantum cryptography. The compromised keying stuff can be affected by the future sessions when provided with security. The public key cryptography systems are retooled with freshly designed algorithms in the coming technology and these tools offers the basic security factors for the quantum key distribution.

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