This document proposes a system for continuous variable quantum key distribution (QKD) using spatial solitons and a wavelength router. Chaotic signals are generated using an optical soliton or Gaussian pulse propagating in a nonlinear microring resonator. These signals can generate large bandwidth continuous wavelengths or frequencies suitable for QKD. The system would allow entangled photons to be generated, enabling continuous variable QKD. Simulation results show specific frequency bands between 500 MHz and 2 GHz could be obtained for QKD using the proposed system integrated into mobile phone networks and handsets.

1. 2010 International Conference on Enabling Science and Nanotechnology (ESciNano),
1-3 December, 2010, KLCC, MALAYSIA
Student Paper
QKD Via a Quantum Wavelength Router Using Spatial Soliton
Mojgan Kouhnavarda, Iraj Sadegh Amiria, Muhammad Arif Jalila, Abdolkarim Afroozeh&,
Jalil AW and Preecha P Yupapin*
b
a Institute of Advanced Photonics Science, ESciNano Research Alliance, Universiti
Teknologi Malaysia (UTM), 81300 Johor Bahru, Malaysia
b Advanced Research Center for Photonics, Faculty of Science King Mongkut's
Institute of Technology Ladkrabang Bangkok 10520, Thailand
*Email:kypreech@kmitl.ac.th
A system for continuous variable quantum key distribution via a wavelength router is
proposed. The Kerr type of light in the nonlinear microring resonator (NMRR) induces the
chaotic behavior. In this proposed system chaotic signals are generated by an optical soliton or
Gaussian pulse within a NMRR system. The parameters, such as input power, MRRs radii and
coupling coefficients can change and plays important role in determining the results in which the
continuous signals are generated spreading over the spectrum. Large bandwidth signals of optical
soliton are generated by the input pulse propagating within the MRRs, which is allowed to form
the continuous wavelength or frequency with large tunable channel capacity. The continuous
variable QKD is formed by using the localized spatial soliton pulses via a quantum router and
networks. The selected optical spatial pulse can be used to perform the secure communication
network. Here the entangled photon generated by chaotic signals has been analyzed. The
continuous entangled photon is generated by using the polarization control unit incorporating into
the MRRs, required to provide the continuous variable QKD. Results obtained have shown that
the application of such a system for the simultaneous continuous variable quantum cryptography
can be used in the mobile telephone hand set and networks. In this study frequency band of 500
MHz and 2.0 GHz and wavelengths of 775 nm, 2,325 nm and 1.55 11m can be obtained for QKD
use with input optical soliton and Gaussian beam respectively.
Recently, Yupapin et al. [1] have shown that the continuous wavelength and frequency can
be generated by using a soliton pulse in a MRR. Suchat et al. have proposed the use of QKD via
optical wireless link, where the secured information i.e., telephone conversation can be achieved
in telephone networks [2]. In this work, we have proposed that the continuous variable QKD
system can be implemented within the mobile telephone handset, where the links can be set up
using the signal bands generated by the technique called chaotic filtering scheme. The schematic
of proposed system to generate optical spatial soliton is shown in Fig. 1. the specified frequency
bands can be obtained by appropriate ring parameters as The optical power is fixed to 550 mW,
fo=2 GHz, no=3.34, n2=2.2xl0-
17
m
2
W- AefFO.50 !lm
2
, a=0.5 dB mm- y=O.I, with 20,000
roundtrips. Fig. 2 shows the graph of the simultaneous frequencies generation, where the related
parameters are R1=10 !lm, 1(1=0.9713, R2=10 !lm, 1(2=0.9718, R3=10 !lm, 1(3=0.9718, R4=15 !lm,
1(4=0.9728. Fig. 3 shows the graph of frequency generation for a down-link converter, where the
parameters used are R1=10 !lm, 1(1=0.9713, R2=10 !lm, 1(2=0.9718, R3=10 !lm, 1(3=0.9718,
R4=15 !lm, 1(4=0.9728. Fig. 4 shows the graph of frequency generation for an up-link converter,
where the parameters used are R1=10 !lm, 1(1=0.9713, R2=10 !lm, 1(2=0.973, R3=10 !lm, 1(3=0.9732,
R4=15 !lm, 1(4=0.9777. In the next stage, the Gaussian beam is input as power is 450 mW, with
centre wavelength at ..10=1.55 !lm, n2=2.2xl0-
15
m
2
W- AefF25 !lm
2
, and other parameters as the
same with before. Result can be shown in Fig. 5. The continuous variable QKD via entangled
photons formation, using localized spatial optical solitons can be connected into a network system
and quantum router shown in Fig. 6. In operation, the large bandwidth within the MRR can be
generated by using an optical soliton or Gaussian pulse input into the device. The localized spatial
soliton pulse is generated whereas the required signals included specific wavelengths or
ESciNano 2010 - http://www.tke.utm.my/mine/escinano2010
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2. 2010 International Conference on Enabling Science and Nanotechnology (ESciNano),
1-3 December, 2010, KLCC, MALAYSIA
frequencies can perform the secure communication network. The security code can be formed by
using the spatial soliton pulses.
References:
[1] P. P. Yupapin, N. Pornsuwanchroen and S. Chaiyasoonthorn, "Attosecond pulse generation
using nonlinear micro ring resonators, " Microwave Opt. Technol. Lett., vol. 50, no. 12, 2008.
[2] S. Suchat, W. Khannam and P. P. Yupapin, "Quantum key distribution via an optical
wireless communication link for telephone networks, " Opt. Eng., vol. 46, pp. 100501-
100502, 2007.
RI R2 R3 R4 "'III Rotatable
A
� Af!O polarizer
Ein EoutJilllL
Fig. I. Schematic of a continuous variable
quantum key distribution, PBS: polarizing beam
splitter; Ds, detectors; Rs, ring radii and Ks,
coupling coefficients.
Fig. 3. Graph simultaneous of specific
frequencies generation, (a) noisy chaotic
signals, (b) frequency bands,(c)fiItering
signals,(d)down-Iink signal(500MHz).
� O�
l··
J.' L-A���p=.!l�MLJ..L�oOL>A�"'--�
€ ' r---�----�----�--�-----------'
lo!'
J. L-__� ���������_
f ::
! °Ol '--__-=__-"'--=- _---::�-'-_=::---"'-�------,='
! ::
L
Fig. 5. Shows the chaotic signals generated
by a series of 4 micro ring resonators.(a), (b),
(c), and (d) show generation of different
wavelengths where R is the radius of the ring
and K is coupling coefficient.
n'.
Fig. 2. Graph simultaneous of specific
frequencies generation,(a) noisy chaotic
signals, (b) frequency bands, (c) filtering
signals, (d) Up-down-Iink signals.
E�t 'L--;':---+-'"--i7"-----.j,��t<-�;-L----t,._____l
� :�
Fig. 4. Graph simultaneous of specific
frequencies generation, (a) noisy chaotic (b)
frequency bands, (c) filtering signals,(d) up-
'(a)
>.
")
ESciNano 2010 - http://w
Fig. 6. Schematic of a large bandwidth signal
generation system (a), and (b) a Schematic of a
wavelength router and network system, where
Rs: ring radii and Ks
,
Ks!' Ks2 are the coupling
coefficients.