Class: Qubit

Inherits:
Object
  • Object
show all
Includes:
QuantumVector
Defined in:
lib/quantum_ruby.rb

Overview

The Qubit class represents quantum bit. They are stored a 2-dimensional column vector. Qubits can be operated on via matrix multiplication or measurement.

Constant Summary collapse

ENTANGLED_WARNING = 
"Alert:  This qubit is entangled.\n\tPlease locate and measure the State\n\tthat contains this qubit's superposition.".freeze

Constants included from QuantumVector

QuantumVector::PRECISION

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from QuantumVector

#==

Constructor Details

#initialize(zero, one) ⇒ Qubit

Takes two values for the superposition of |0> and |1> respectively and store it in a Qubit Values must obey the normalization constraint



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# File 'lib/quantum_ruby.rb', line 120

def initialize(zero, one)
  @vector = Matrix[[zero], [one]]
  normalized?
end

Instance Attribute Details

#entangled ⇒ Object

Returns the value of attribute entangled.



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# File 'lib/quantum_ruby.rb', line 111

def entangled
  @entangled
end

#vector ⇒ Object

Returns the value of attribute vector.



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# File 'lib/quantum_ruby.rb', line 110

def vector
  @vector
end

Instance Method Details

#measure ⇒ Object

Measurement can only happen at the expense of information elsewhere in the system. If two qubits are combined then their combined state becomes dependent so doing something to one can affect the other. This applies both to further operations or measurement. After measurement all related qubits’ superpositions collapse to a classical interpretation, either 0 or 1

Qubit.news(1, 0).to_s # 0, qubit remains the same
Qubit.news(0, 1).to_s # 1, qubit remains the same
Qubit.new(1/Math.sqrt(2), 1/Math.sqrt(2)) # either 0 or 1 and qubit superposition collapses
                                            to look like one the above qubits depending on the outcome



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# File 'lib/quantum_ruby.rb', line 134

def measure
  if rand < @vector[0, 0].abs2
    @vector = [1, 0]
    0
  else
    @vector = [0, 1]
    1
  end
end

#state ⇒ Object

Return the qubit’s superposition as a pretty printed array

Qubit.news(1, 0).state
#   [1
#    0]



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# File 'lib/quantum_ruby.rb', line 149

def state
  return if entangled?

  super
end

#to_s ⇒ Object

Returns the qubit’s superposition in Bra-Ket notation

Qubit.news(1, 0).to_s # 1|0>
Qubit.news(0, 1).to_s # 1|1>
Qubit.new(1/Math.sqrt(2), 1/Math.sqrt(2)) # 0.707|0> + 0.707|1>



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# File 'lib/quantum_ruby.rb', line 160

def to_s
  return if entangled?

  first = el(0)
  last = el(1)

  out = ''
  out << first.to_s << ZERO_KET unless first.zero?
  out << ADD_SYM                unless first.zero? || last.zero?
  out << last.to_s << ONE_KET   unless last.zero?
  out
end