edu.buffalo.fs7.mathlib
Class Decoherence

java.lang.Object
  |
  +--edu.buffalo.fs7.mathlib.MathObject
        |
        +--edu.buffalo.fs7.mathlib.MathMap
              |
              +--edu.buffalo.fs7.mathlib.Decoherence

All Implemented Interfaces:

java.lang.Cloneable

public class Decoherence

extends MathMap

class representing the effect of decoherence. The decoherence model implemented is assuming that at every time a decoherence effect is about to occur a random qubit interacts with an environmental qubit through the following process:

|0>|0> --> |0>|0> and |1>|0> --> sqrt(p)|1>|0> + sqrt(1-p)|0>|1>

where p is the probability that the qubit stays in the state |1> and 1-p the probability that it decays to |0>. After a decay the state is renormalized. The underlying assumption is that the state |1> is higher energetic than |0> and therefore a decay is possible.

Field Summary

static int

presetQubit

Fields inherited from class edu.buffalo.fs7.mathlib.MathObject

mathlib

Constructor Summary

Decoherence()
create a measurement map for a full measurement

Method Summary

MathObject	apply(double rate, double decay, MathObject o)
MathObject	apply(MathObject o) applies a decoherence step to a ket vector.
static boolean	decayOccurred() returns true if at the last operation the qubit decayed
static boolean	decohere(Braket q, double p, int qubit) this method decoheres a given qubit in the ket given as well.
static int	getLastDecoheredQubit() returns the last decohered qubit.
java.lang.String	toString() string representation of the decoherence map

Methods inherited from class edu.buffalo.fs7.mathlib.MathObject

clone, toParseableString

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

presetQubit

public static int presetQubit

Constructor Detail

Decoherence

public Decoherence()

create a measurement map for a full measurement

Method Detail

apply

public MathObject apply(double rate,
                        double decay,
                        MathObject o)

apply

public MathObject apply(MathObject o)

applies a decoherence step to a ket vector. In this method a random number is generated and compared to the error rate per gate (this value right now is obtained from the circuit_properties variable). If the random number is smaller the method decohere is called with a random qubit and the decay probability specified by the ciruit_properties variable.

Overrides:

apply in class MathMap

Parameters:

o - Braket

decohere

public static boolean decohere(Braket q,
                               double p,
                               int qubit)

this method decoheres a given qubit in the ket given as well. With probablity p the qubit remains in state |1>. The state is renormailzed afterwards.

Parameters:

q - ket vector

p - probability for the state |1> remaining in |1>

qubit - the qubit to decohere

Returns:

true if a decay occured

See Also:

BinaryOp.implicitApply(Gate, Braket, Matrix)

getLastDecoheredQubit

public static int getLastDecoheredQubit()

returns the last decohered qubit. -1 if nothing happend during last decoherence step

decayOccurred

public static boolean decayOccurred()

returns true if at the last operation the qubit decayed

toString

public java.lang.String toString()

string representation of the decoherence map

Overrides:

toString in class MathObject

Following copied from class: edu.buffalo.fs7.mathlib.MathObject

See Also:

MathObject.toParseableString()